Rockwell Automation 1771-KA2 User Manual

Download

able of Contents

Introduction 1-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Description 1-1 About Organization 1-5 Chapter Summary

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

This Manual

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-3

1-5

Station Hardware 2-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General 2-1 Communication Processor 2-8 I/O Chassis Power Cables 2-13 Other Chapter Summary

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Adapter Module

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Supply

Optional Equipment

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-2

2-9

2-10

2-13 2-13

Module Installation 3-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General 3-1 Switch Keying 3-7 Installation Cable

Commands 4-1

General 4-1 Protected/Unprotected 4-3 Write Commands Bit Write Commands Read Command Accessible Accessible Accessible Accessible Chapter Summary

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Settings

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Connections

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

In The I/O Slot

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Data T

able Locations - PLC-2 Processors

Data T

able Locations - PLC Processors

Data T

able Locations - PLC-3 Processors

Data T

able Locations - PLC-4 Microtrol Processors 4-1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . .

. . . . . . . . . . .

3-1

3-8 3-9

4-4 4-5 4-7 4-7 4-9

4-10

4-15

Communication Zone Rungs 5-1 . . . . . . . . . . . . . . . . . . . . . . . . . .

General 5-1 Header Rungs Memory Access Rungs Command Rungs Delimiter Chapter Summary

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Rung

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-3 5-4 5-7

5-1

5-12

able of Contents

Status Words 6-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General 6-1 START/DONE Word REMOTE/LOCAL Error Chapter Summary

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

AULT Word

Code Storage W

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ord

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6-2 6-3 6-5 6-7

Command Initiation, Execution, and Monitoring 7-1 . . . . . . . . . . .

General 7-1 START/DONE Controlling REMOTE/LOCAL Timeout Preset Value Chapter Summary

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Bit T

iming

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The Start Bit

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

AUL

T Bit Monitoring

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-1

7-4 7-10 7-14 7-19

Station Interfacing 8-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General 8-1 Floating Master Commands From A Computer Chapter Summary

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1

8-5

8-9

Start-up and Troubleshooting 9-1 . . . . . . . . . . . . . . . . . . . . . . . . .

General 9-1 Start-up Start-up Procedures Troubleshooting 9-18 Chapter Summary

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

and T

roubleshooting Aids

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9-1 9-12

9-23

Design Aids and Documentation 10-1 . . . . . . . . . . . . . . . . . . . . . . .

General 10-1 Program Summary Forms 10-2 Memory Maps

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10-1

10-2

Error Code Listing A-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction

Chapter

Description

An Allen-Bradley Data Highway extends the capabilities of programmable controllers by letting them exchange data with each other and with other intelligent RS-232-C devices. Data Highway integrates individual controllers into a larger automated manufacturing network. On a single Data Highway cable, as many as 64 separate programmable controllers and computers can be connected over a distance of 10,000 feet (3,048m).

The unit that interfaces PLC-2 family programmable controllers to this network, and makes communication possible, is an A-B Communication Adapter Module (cat. no. 1771-KA2). (See Figure 1.1) It is a Data Highway station interface module and is used with Bulletin 1772 programmable controller processors. These processors are:

PLC-2 Processor (cat. no. 1772-LR) PLC-2/20 Processor (cat. no. 1772-LP1, -LP2) PLC-2/30 Processor (cat. no. 1772-LP3)

Figure 1.1 Communication

Adapter Module (cat. no. 1771-KA2)

10862-I

Mini-PLC-2 Processor (cat. no. 1772-LN1, -LN2, -LN3) Mini-PLC-2/05 (cat. no. 1772-LS, LSP)

1–1

Chapter 1

Introduction

Mini-PLC-2/15 (cat. no. 1772-LV)

This module enables communication of memory data between these processors, and from any of these processors to other processors on the Data Highway via communication adapter modules.

A typical Data Highway configuration is shown in Figure 1.2.

Figure 1.2 Representative

10,000 feet (3,048 meters) maximum

Data Highway Cable Trunkline

Data Highway Configuration

1770-SC Station Connector

Mini-PLC-2, Mini-PLC-2/05, or Mini-PLC-2/15 Programmable Controller

Cable Droplines 100 feet (30.5 meters) maximum

I/O Rack

Communication Adapter Module (cat. no. 1771-KA2)

PLC-2 Family Programmable Controller

Communication Adapter Module (cat. no. 1775-KA)

PLC-3

Communication Controller Module (cat. no. 1771-KE/KF)

Mini Computer

12210

About This Manual

1–2

The terms “communication adapter module” and “1771-KA2” and “KA2” are interchanged throughout the manual.

Chapter 1

Introduction

This manual describes installation, operation, and programming necessary to use the KA2 communication adapter module. Use this manual with the other manuals and publications pertinent to your system. Table 1.A lists other available Data Highway manuals and Table 1.B lists PC manuals.

able 1.A

Data

Highway Documentation

Old

Publication

Number

1774-819 1774-6.5.8 User’

1771-822 1771-6.5.15 User’

1771-823 1771-6.5.16 User’

1773-801 1773-6.5.2 User’

1775-802 1775-6.5.1 User’

1771--811 1771-6.5.8 User’

1770-810 1770-6.2.1

New

Publication

Number

Module (cat. no. 1771-KA)

Module (cat. no. 1771-KE/KF)

Module (cat. no. 1771-KX1)

Communication Interface Module (cat. no. 1773-KA)

Module (cat. no. 1775-KA)

Interface Module (cat. no. 1771-KG) Data Highway Cable Installation Manual

Title

s Manual, Communication Adapter

s Manual, Communication Controller

s Manual, PROVOX system Interface

s Manual, PLC-4 Microtrol

s Manual, Communication Adapter

s Manual, PLC-2 Family/RS-232-C

1–3

Chapter 1

Introduction

able 1.B

Manuals for Allen-Bradley Programmable Controllers

Old

Controller

Mini-PLC-2 Program. Cont.

Mini-PLC-2/05 1772-830

Mini-PLC-2/15 Program. Cont.

PLC-2/20 Program. Cont.

PLC-2/30 Program. Cont.

PLC Program. Cont.

PLC-3 Program. Cont.

PLC-4 Microtrol

Number

1772-820 1772-821

1772-831 1772-803

1772-804 1772-807

1772-802 1772-807

1772-806 1774-812

1774-800 1775-800

1775-801 1773-800 1773-6.5.1

New

Number

1772-6.6.3 1772-6.8.4

1772--6.6.6 1772-6.8.6

1772-6.6.1 1774-6.8.2

1772-6.6.2 1772-6.8.1

1772-6.6.2 1772-6.8.3

1774-6.6.2 1774-6.8.1

1775-6.7.1 1775-6.4.1

Manual TItle

Assembly and Installation Programming and Operation

Assembly and Installation Programming and Operations

Installation and Operations Programming

Product Guide

To use this manual, 1772-6.5.1, knowledge of the particular progammable controller being used in your application is essential. Because you connect the communication adapter module to an operating programmable controller, you must have a good understanding of programmable controller operation, installation, memory structure, and programming.

1–4

Publications are available for each Allen-Bradley programmable controller. All publications in Table 1.A and Table 1.B are available from an A-B sales office, or from Allen-Bradley Publications, 6100 Industrial Court, Greendale, WI 53129.

Features of a 1772-KA2

Here are some of the KA2’s features: New commands have been added to the 1771-KA2 that simplify

upload and download procedures.

A KA2 lets you to change (remotely) the size of the PC data table.

(New with 1772-KA2 module.)

It has second module or “daisy chain” capability. (New with 1772-KA

2 module.) Uses ladder diagram instructions for ease of programming. Offers memory write protection through programming and switch

selection.

Chapter 1

Introduction

Controls communication without need for a host computer. Has automatic error checking of data it receives. Has self-checking diagnostics. Shows status and diagnostics with LED indicators and error codes. Controls DONE and REMOTE/LOCAL FAULT memory bits as status

and diagnostic indicators. Automatically re-tries messages. Automatically recovers from master station fault condition. Has selectable priority levels for commands. Is compatible with industrial terminal system. Installs easily.

Organization

Chapter Summary

The chapters in this manual are organized as follows and each chapter closes with a summary:

Chapter 2 describes the hardware components that make up a Data

Highway station. Chapter 3 outlines procedures for module installation. Chapter 4 describes programmed commands and memory access. Chapter 5 describes programming of the communication zone of

program. Chapter 6 describes status words that are controlled by the module at

its station processor. Chapter 7 outlines programming that is necessary to initiate and

monitor command execution. Chapter 8 describes station interface module interaction along the Data

Highway. Chapter 9 describes start-up and troubleshooting tools and procedures. Chapter 10 provides aids to design and documentation of a Data

Highway that uses a communication adapter module.

This chapter discussed:

Features of a 1771-KA2 Communication Adapter Module How the module fits into an A-B Data Highway system What a 1771-KA2 does, and the A-B PLC data processor it works with Publications available for Data Highway and PLC-2 family PCs

In chapter 2 you will learn about a Data Highway station and the KA2’s role in station function.

1–5

Chapter 1

Introduction

1–6

Station Hardware

Chapter

General

The following components make up a Data Highway station with a PLC-2 family PC:

Communication Adapter Module Processor PLC-2 I/O adapter module for PLC-2/20 and PLC-2/30 processors Bulletin 1771 I/O chassis Power supply Data Highway/Processor cable Data Highway cable dropline

Figure 2.1 shows the configuration of a typical Data Highway station for PLC-2/20 and PLC-2/30 processors. Figure 2.2 shows a typical configuration for the mini-processor module.

Figure 2.1 Typical

Station Configuration--PLC-2/20 and PLC-2/30 Processors

Data Highway Cable Trunkline

Station

Processor

I/O Chassis

Data Highway Processor Cable (cat. no. 1771-CR)

Station Dropline 100 feet maximum

Communication Adapter Module (cat. no. 1771-KA2)

12326

2-1

Chapter 2

Station Hardware

Figure 2.2 Typical

Station Configuration--Mini-PLC-2, Mini-PLC-2/05, and Mini-PLC-2/15 Controllers

Data Highway Cable Trunkline

Station

Mini-Processor Module (cat. no. 1772-LV, -LS, -LSP; 1772-LN1, -LN2, -LN3)

System Power Supply

Data Highway Processor Cable (cat. no. 1771-CN.-CO)

Communication Adapter Module (cat. no. 1771-KA)

Station Dropline

Connection for Programming Terminal

12327

As these figures illustrate, the term “station” combines both the communication adapter module and its connected programmable controller processor. (When specifying only the individual processor or communication adapter module at a station, the terms “station processor” or “station communication adapter module” are used.)

Communication Adapter Module

2-2

The following sections describe the functions and compatibility of each station hardware component.

A communication adapter module (cat. no. 1772-KA2) provides the interface between all PLC-2 family PCs and other stations on the Data Highway. (Refer to Figure 2.3). The module has sockets for cable

Chapter 2

Station Hardware

connection, switches for enabling or disabling specific module operations, and indicators to aid in monitoring module behavior and in troubleshooting. Subsequent sections describe each of these parts of the module and other aspects of module hardware that are significant in its set-up and installation.

Each communication adapter module in a Data Highway installation must have a unique station number. This station number is used to address commands to the module from other stations.

Figure 2.3 Communication

Adapter Module (cat. no. 1771-KA2)

(Side view)

Indicator

Connectors

10862-I

Switch Cover

Connectors

The front of a 1772-KA2 module has 3 cable connectors labeled:

DATA HIGHWAY PROGRAM INTERFACE PROCESSOR

See Figure 2.4.

2-3

Chapter 2

Station Hardware

Figure 2.4 Module

“Program Panel” or “Interface” Socket on Processor

Connection Summary

Data Highway Cable (User-Assembled)

Program Panel Interconnect Cable (Cat. no. 1772-TC)

Data Highway Processor Cable (cat.no. 1771-CN, -CO, -CR)

Industrial Terminal System (cat. no. 1770-T1 and T2)

Data Highway Connector

The upper connector of the module accepts the 15-pin Data Highway dropline cable. Through this connection, a single KA2 module can communicate with as many as 63 other Data Highway stations.

Module transmitting and receiving circuitry on this channel are transformer-coupled to the Data Highway link. This design permits differential transmission of data with high common-mode noise immunity. Electrically, transformer coupling provides isolation between module logic circuitry and the Data Highway cable.

Program Interface Connector

10863-I

2-4

The middle outlet on the module connects to an industrial terminal system (cat. no. 1770-T1, -T3), or to a second KA2, or to a 1771-KG series B module.

Chapter 2

Station Hardware

To connect any programming terminal to the PROGRAM INTERFACE connector, use a program panel interconnect cable (cat. no. 1772-TC).

With a 1772-KA2 module installed, the PROGRAM INTERFACE connector substitutes for the PROGRAM PANEL connector on PLC-2/20 or PLC-2/30 processors or the INTERFACE socket on the Mini-PLC-2, Mini-PLC-2/05, or Mini-PLC-2/15. This means that all interaction between the processor and the programming terminal is controlled through the communication adapter module. This interaction includes program entry and any functions that involve peripheral devices except cassette loads--including report generation, contact histograms, and generation of program copies on paper or on punched tape.

The communication rate over this channel is 9600 baud. Optical-electrical isolation is provided between receiving circuitry on this channel and module logic circuitry.

NOTE: The PROGRAM INTERFACE connector need not connect to a programming terminal for the module to operate. This connector serves as a programming terminal connection whenever such a device is needed for program entry, editing or monitoring.

Processor Connector

The lower connector of the module connects to the station PLC-2/20 or PLC-2/30 processor, or Mini-processor module. (Refer to Figure 2.1 and Figure 2.2) A Data Highway/Processor cable, described in section titled “Cables,” is used for this connection.

Indicators

There are 5 LED indicators on the front of the module, as seen in Figure 2.5.

These indicators are useful for monitoring module activity and for troubleshooting. Three green indicators show module status during normal receiving and transmitting of messages. Two red indicators show the status of module diagnostics.

2-5

Chapter 2

Station Hardware

Figure 2.5 Module

Indicators

COMM

ADAPTER

Transmitting Receiving Message Ready

Program Status Processor Link

Status

XMTG RCVG RDY

PROG PROC

XMTG

The green transmitting indicator turns on when the module is current master of the Data Highway. When this indicator is on, therefore, the communication adapter module is transmitting messages on the Data Highway communication link, or it is polling.

RCVG

The receiving indicator turns on when the module is receiving a message addressed to it. Otherwise, RCVG is off.

When both the RCVG and XMTG indicators are on, the module is current master of the Data Highway and is polling. (The section titled “Polling,” in chapter 8, describes polling procedure.)

2-6

RDY

The green message ready indicator turns on when the module has messages ready to transmit. With this indicator on, the module is ready to assume mastership when it is polled.

Chapter 2

Station Hardware

PROG

The red program status indicator tells you the status of module checks on the communication zone rungs of the user program. (The section titled “Overall Format,” chapter 5, describes these rungs.) The module first checks these rungs at power-up. When it locates the header rung of this zone, the module turns the PROG indicator on. After it checks the rungs, provided no errors are found, the module turns the PROG indicator OFF. However, if the module detects any programming error in the communication zone of the program, this indicator remains ON. In this event, the module cannot function. You must check the communication zone of the program and correct any errors. (Start-up procedures are described in chapter 9.)

PROC

The red processor link status indicator gives the status of error-checking diagnostics for communication adapter/processor communication. The PROC indicator is normally off.

Should the 1771-KA2 module detect an error in data transmission with the processor, it turns the PROC indicator on. This may mean one of the following:

Disconnection of the Data Highway/Processor cable between the

communication adapter and the processor Fault in processor operation Incorrect selection of processor link communication rate on the module

(Refer to section titled “Write Option Switch Assembly,” chapter 3).

The section titled “Module Indicators,” in chapter 9, describes the use of indicators in troubleshooting.

Switches

There are 3 sets of switches on the 1771-KA2 module circuit board. These switches are beneath the small switch cover plate on the component-side cover of the module. (Refer to Figure 2.3).

The programmer selects the settings of these switches for each communication adapter module, based upon such variables as station number, command capabilities, and type of station processor. Switch settings are a part of module installation, described in chapter 3.

2-7

Chapter 2

Station Hardware

Module Specification Summary

Table 2.A lists operating specifications for a 1771-KA2 module.

able 2.A

Operating

Specifications

Function

Interface entire PLC-2 family

•

programmable controller to the Data Highway

Location

Bulletin 1771 I/O Chassis (any slot

•

except furthest left)

Communication Channels

• T

o Data Highway

• T

o programming terminal or second

module in daisy chain

• T

o processor or first module in daisy

chain

Communication Rates

• T

o Data Highway: 57.6k baud

(Recommended)

• T

o programming terminal or second

module: 9.6k buad

• T

o processor: 91.2k baud for processor (except PLC-2, cat. no. 1772-LR); 9.6k baud for first communication module or PLC-2family processor

Compatible Power Supplies

•

System power supply (cat. no. 1771-P1)

•

Auxiliary power supply (cat. no. 1772-P2)

•

System power supply module (cat. no. 1772-P1, series B or later)

•

Auxiliary power supply (cat. no. 1772-P2 series B or later)

•

Power supply module 1771-P3

•

Power supply module 1771-P4

•

Power supply module 1771-P5

Ambient T

• 32o to 140oF (0o to 60oC) (operational)

• -40o to 185oF (-40o - 85oC) (storage)

Humidity Rating

•

Keying

•

Power Supply Requirement

•

emperature Rating

5% to 95% (without condensation)

Module slotted for I/O chassis keying band positioning.

Positions 4-6, 22-24

+5V DC at 1.2A (max.)

Processor

2-8

This manual uses the term “processor” as a general term for any of the PLC-2 family processors. Individual processors are specified only when some distinction must be made.

The normal operating sequence of the station processor is not changed by a communication adapter module, that is, the processor carries out its scan of input and output modules and execution of the user program as though the communication adapter module weren’t there.

Chapter 2

Station Hardware

The interaction between a KA2 module and its station processor occurs in memory control. The station KA2 can read data from and write data into processor memory, based on various user-programmed commands. Commands that originate at a station communication adapter module can control only data table areas of processor memory. Commands generated by a computer that is connected to the Data Highway through a communication controller module (cat. no. 1771-KE/KF) can control both data table and user program memory areas.

Note that the processor continues to execute the user program and to control output devices, whether or not the station communication adapter module is in operation. Thus, disconnection of the Data Highway cable or faulted operation of the communication adapter module does not cause shutdown of the station processor.

I/O Chassis

A-B designed the 1771-KA2 module to fit in a Bulletin 1771 I/O chassis assembly (cat. no. 1771-A1,-A2,-A4). This chassis houses Mini-PLC-2, Mini-PLC-2/05 and Mini-PLC-2/15 programmable controllers. With one of these controllers, you can use any unoccupied I/O slot for communication adapter modules.

With PLC-2/20 and PLC-2/30 programmable controllers, use a Bulletin 1771 I/O chassis as an I/O rack. In this case, the 1771-KA2 module can be installed in any chassis slot except the one furthest left. This left-most slot must be occupied by a PLC-2 I/O adapter module (cat. no. 1771-AL or 1771-AS), shown in Figure 2.6, or a backplane jumper board assembly (cat. no. 1771-EY).

A Bulletin 1771 I/O chassis is usually mounted within an enclosure. We recommend proper grounding of this enclosure because it minimizes the effect of noise from the surrounding industrial environment. (Grounding procedures for the Bulletin 1771 I/O chassis are described in publication 1772-6.6.3).

2-9

Chapter 2

Station Hardware

Figure 2.6 1771-AL

Adapter Module

Power Supply

PLC-2

I/O ADAPTER

10864-I

A 1771-KA2 module gets its power from the backplane. It requires +5V DC at 1.2 amperes (max.). The following power supplies are compatible:

System power supply (cat. no. 1771-P1) Auxiliary power supply (cat. no. 1771-P2) PLC-2 system power supply module (cat. no. 1772-P1, series B or

later)

PLC-2 auxiliary power supply (cat. no. 1777-P2, and 1777-P4 series B

or later)

Modular power supplies (cat. no. 1771-P3, -P4, -P5)

You must connect one of these supplies to the I/O chassis that contains the KA2 communication adapter module. In a Mini-PLC-2, or a Mini-PLC-2/15 this is the system power supply, shown in Figure 2.7. In a Mini-PLC-2/05, you must use a 1771-P3, -P4, or P5 power supply.

2-10

Figure 2.7 1771-P1

Chapter 2

Station Hardware

System Power Supply

Battery Low

DC ON

ALLEN-BRADLEY

10865-I

When using the PLC-2/20 or PLC-2/30 processor, any of these supplies can power the I/O chassis so long as core memory is not being used. (Refer to processor manuals.) An auxiliary power supply (cat. no. 1771-P2) closely resembles the system power supply shown in Figure 2.7. PLC-2 power supply module (cat. no. 1772-P1) is not a separate unit, but is enclosed within the metal chassis of the PLC-2/20 or PLC-2/30 processor.

PLC-2 power supplies must be series B or later for communication adapter module compatibility. On both of these supplies, a label on the front edge of the circuit board identifies the series level. To locate this label, remove AC power from the supply and remove the metal front plate that covers the module. If the label shows the catalog number but not the series level, the module is series A. Otherwise, series B or later is indicated.

2-11

Chapter 2

Station Hardware

Figure 2.8 PLC-2

Power Supplies

AC FUSE

PLC

PLC 2/30

2/30

a. PLC-2 System Power Supply Module

AC FUSE

10236-I

10236a-I

2-12

b. PLC-2 Auxiliary Power Supply

Chapter 2

Station Hardware

Cables

A 1771-KA2 module requires the following cables for installation:

Data Highway/Processor cable (cat. no. 1771-CN,-CO,-CR) User-assembled Data Highway cable

Figure 2.1 and Figure 2.2 show the connections made with these cables.

You can order Data Highway/Processor cables in 3 lengths:

1.5 ft. (cat. no. 1771-CN)

3.5 ft. (cat. no. 1771-CO)

10.5 ft. (cat. no. 1771-CR)

The 2 shorter cables are intended for connection to a Mini-PLC-2, Mini-PLC-2/05, or Mini-PLC-2/15 module. A 10.5 ft. cable is used with PLC-2, PLC-2/20 or PLC-2/30 processors.

You must assemble and install your own Data Highway cable, dropline and trunkline segments. A separate publication, Data Highway Cable, Assembly and Installation Manual, publication 1770-6.2.1, gives information on layout, make-up, and installation of the cable.

Other Optional Equipment

Chapter Summary

In addition to the components shown in Figure 2.1 and Figure 2.2, you can install your own equipment at or near the Data Highway station. The chief purpose of additional components is to provide diagnostic or monitoring information. Such devices as alarms, displays and indicators can be controlled from output modules of the programmable controller to provide operating or fault information to plant personnel.

Minimally, a single indicator should be installed to alert your personnel to a REMOTE or LOCAL FAULT condition that prevents normal message transfer. The significance of REMOTE/LOCAL FAULT bits, and the recommended programming to monitor these bits, is described in chapter

This chapter told you the:

Components of an A-B Data Highway system Role of a 1771-KA2, its connectors, switches, and indicators Specs of a 1771-KA2 Where a KA2 resides and how it is connected to its station Optional equipment possibilities at a Data Highway station

In chapter 3 you will read about KA2 switches and installation.

2-13

Chapter 2

Station Hardware

2-14

Module Installation

Chapter

General

Switch Settings

This chapter outlines procedures for preparation, installation, and connection of a 1771–KA2 module. Before performing these procedures, you should check component compatibility and the station set–up recommendations in chapter 2.

There are 3 sets of switches on a 1771–KA2 circuit board:

Write option switch assembly Station no. switch group Data Highway baud rate switch assembly

Refer to Figure 3.1. The switches at each station communication adapter module must be set as the programmer specifies. To access these switches, loosen the two screws that hold the small cover plate to the side of the module. Then, rotate this cover plate to expose the switches.

Figure 3.1 Module

Switches

Write Option

Switch Assembly

12345

O N

O F F

O N

O F F

O N

O F F

O N

O F F

Station Number Switch Group

O N

O F F

Data Highway Baud Rate Switch Assembly

12329

3-1

Chapter 3

Module Installation

Use the tip of a ball–point or other pointed instrument to set these switches. Do not use a pencil, as lead could jam the switch.

For troubleshooting purposes, we recommend that the programmer document the required switch settings for each 1771–KA2. Use form 5030, in chapter 10, to record switch settings for the module at each station. That way, should replacement of the module be required, switches on the replacements can be set quickly.

Write Option Switch Assembly

The first rocker switch assembly from the left is the write option switch assembly. (Refer to Figure 3.2). In this assembly, switches numbered 1 through 5 enable or disable different types of write and bit write commands from being received by, or sent from, the communication adapter module. (Note that the unprotected read command is not affected by any of these switch settings.) Switch no. 6 enables and disables daisy chain operation. See FIRST/SECOND MODULE at end of this section.

Figure 3.2 Write

Option Switch Assembly

Execute Unprotected Write Commands

Receive Protected Commands

O N

O F F

Send Unprotected Commands

* After revision D, the name and function of switch 3 changed to ”Execute download in RUN program.”

3456

Shutdown / Auto Restart*

• On–Shutdown

• Off–Auto Restart

Received Priviledged Write

Enable/Disable

• On–First Module

• Off–Second Module

The following paragraphs describe settings for these switches.

RECEIVE PROTECTED COMMAND SWITCH

12330

3-2

Switch no. 1 of the write options switch assembly determines whether the module is enabled to receive and execute protected write and bit write commands from other stations. Set this switch as follows:

Chapter 3

Module Installation

ON – Enables execution of received protected commands. OFF – Disables received protected commands.

Note that both an ON setting of this switch and a memory access rung are required to allow execution of received protected commands. (Memory Access rungs are described in chapter 5.)

This switch does not prevent the module from receiving and executing unprotected commands from another station. (A separate switch, described subsequently, enables or disables execution of received unprotected commands.)

EXECUTE UNPROTECTED WRITE COMMANDS SWITCH

Switch 2 determines whether the module can receive and execute unprotected write and bit write commands from other stations. Set this switch as follows:

ON – Enables received unprotected write and bit write commands to

be executed.

OFF – Disables the module from executing received unprotected write

and bit write commands

Note that this switch does not disable unprotected read commands from being received and executed by the module.

SHUTDOWN/AUTOMATIC RESTART SWITCH

On modules before revision D, switch 3 presents the option, after a hard error, of restarting the 1771–KA2, or shutting it down.

ON – Shuts down the module OFF – Automatically restarts itself

When a hard error occurs it normally indicates fairly severe communication problems that should be corrected before starting. Such errors usually involve bad cabling or noise.

REVISION D

The third switch in the Write Option Switch assembly on the 1771–KA2 module (formerly the Shutdown/Automatic Restart Switch) will change function for revision D and become the Execute Download in Run Program switch.

3-3

Chapter 3

Module Installation

RECEIVE PRIVILEGED WRITE SWITCH

Switch 4 determines whether the module can execute received privileged write commands. These commands can be issued only from a computer connected through a communication controller module (cat. no. 1771–KE/KF).

These commands give the computer the capability to alter the user program memory of the station processor. Set this switch as follows:

ON – Enables a 1771–KA2 to execute received privileged write

commands

OFF – Disables the 1771–KA2 from executing received privileged

write commands.

SEND UNPROTECTED COMMANDS SWITCH

Switch 5 determines whether the module can send unprotected write or bit write commands to another station. Set this switch as follows:

ON – Enables the module to send unprotected write and bit write

commands

OFF – Disables the module from sending unprotected write and bit

write commands

This switch does not prevent unprotected read commands from being sent by a communication adapter module.

FIRST/SECOND MODULE

Use switch 6 for first/second module selection. Set switch:

ON – Use this setting when connected directly to any compatible

processor except PLC–2 (1772–LR).

OFF – Use this setting when the KA2 module is connected to a

PLC–2 (1772–LR), a 1771–KG series B module, or another KA2 module.

3-4

Station No. Switch Group

You must designate a unique station number for each communication adapter module on a Data Highway. This designation is made by the programmer and switch–selected on the station number switch group of the module.

Chapter 3

Module Installation

The station number switch group comprises 3 switch assemblies (SW2, SW3, SW4) on the module circuit board, as Figure 3.3 indicates. These switches determine the station number of each communication adapter module.

SWITCH SETTING

No. 1 No. 2

OFF OFF OFF ON ON OFF ON ON

a. First Digit

The station number is a 3–digit octal number from 010 110

–3768. Each of the 3 switch assemblies in this group is set to

represent an individual digit of this station number. Figure 3.3 shows the combination of switch settings for each digit.

Figure 3.3 Station

Number Switch Settings

O N

O F F

SW2 SW3 SW4

O N

O F F

DIGIT

0 1 2 3

O N

O F F

No. 1 No. 2

OFF OFF OFF OFF OFF ON OFF ON ON ON ON ON

b. Second and Third Digits

–077

OFF

SWITCH SETTING DIGIT

No. 3

OFF ON OFF

ON OFF OFF ON ON

OFF

0 1 2 3 4 5 6 7

OFF

12331

3-5

Chapter 3

Module Installation

In this binary–coded octal numbering arrangement, each switch has an associated binary value: 1, 2, or 4 if set ON, 0 if set OFF. The value of each individual digit of the station number is the sum of the binary values in its corresponding switch assembly. Table 3.A gives an example for the settings of this switch group.

able 3.A

Switch

Setting Example: Station No. 037

STATION

NO. DIGITS

SWITCH NO. SWITCH

SETTING

0 3 7

1 2 1 2 3 1 2 3

OFF OFF OFF ON ON ON ON ON

Note that the switches allow a range of station numbers from 0008 to 377 (256 possible numbers). However, there are practical reasons for using the the range 010

–077

and 110

–3768. These station numbers are

addressable from any station using an industrial terminal. PLC–2 family programmable controllers cannot address 000 Also, station 377

is an illegal address on the Data Highway. To optimize

response times, use consecutive station numbers beginning with 010

to 0078 or 1008 to 1078.

Data Highway Baud Rate Switch Assembly

The switch assembly labeled SW5 on the module circuit board is the data highway baud rate switch assembly. (Refer to Figure 3.4). The switches in this assembly must be set for the baud rate being used on the Data Highway communication link.

Figure 3.4 Data

Highway Baud Rate Switch Assembly

3-6

O N

O F F

Both switches ON for

57.6K Baud Rate

Chapter 3

Module Installation

The module is shipped with these switches set for 57.6K baud. Both switches are set ON for this communication rate. This baud rate is the intended Data Highway communication rate.

CAUTION: Do not set these switches for any other baud rate. Incorrect setting of these switches may cause faulted data transmission on the Data Highway communication link. This may disable Data Highway operation until the switch setting is corrected.

After rechecking all switch settings, replace the cover plate on the module.

Keying

The I/O slot designated for the 1771–KA2 communication adapter module should be keyed to admit only that module. Plastic keying bands, shipped with the I/O chassis, accomplish this purpose. These keying bands provide for only one type of module in a slot.

On the rear edge of the communication adapter module are 2 slots. Position the keying bands on the backplane connector to align with these slots. For the communication adapter module, position keying bands on the upper backplane connector between these numbers printed on the backplane:

4 and 6 22 and 24

Refer to Figure 3.5. Use needle–nose pliers to insert or remove keying bands.

3-7

Chapter 3

Module Installation

Figure 3.5 Keying

Band Position

Keying Bands

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

Installation In The I/O Slot

Follow these procedures to install the module:

1. Turn I/O chassis power off. (This refers to the power supply that

connects to the I/O chassis at its backplane.

CAUTION: To avoid module damage, always be certain that power to the I/O chassis is off before insertion or removal of the KA2.

2. Insert the keying bands, as described in section titled “Keying.”

3. Insert the module into its designated slot. Plastic tracks on the top

and bottom of the slot guide the module into position. Do not force the module into its backplane connectors. Rather, apply a firm, even pressure to seat the module in its slot.

4. Snap the plastic chassis latch over the module. This secures the

module firmly in the I/O chassis.

3-8

Chapter 3

Module Installation

Cable Connections

The following cable connections are made to a communication adapter module:

Data Highway cable Program panel interconnect cable (cat. no. 1772–TC) Data Highway/Processor cable (cat. no. 1771–CR, –CO,–CN)

At set up, all cable connections to the module can be made with power on. After the program is up and running, however, it is safer to make connections with power off because of the possibility of noise that connecting will make. Also, again after the program is running, a module should only be connected to a Data Highway with power off. A powered–up module that is disconnected from the Data Highway will be in the polling state and cause a highway fault if it is re–connected. This is the same as connecting two active highway segments (which also should not be done).

Data Highway Connection

The module connects to the Data Highway communication link by means of a user–assembled dropline. This dropline connects to the trunkline of the Data Highway at a 1770–SC station connector (Figure 3.6), or a 1770–XG tee connector.

3-9

Chapter 3

Module Installation

Figure 3.6 Data

Highway Cable Connection

1770–SC Station Connector

Trunkline

Dropline (100 feet maximum)

Communication Adapter Module (cat. no. 1771–KA2)

Program Panel Interconnect Cable Connection

The center connector of the communication adapter module is labeled PROGRAM INTERFACE. When the module is installed and connected to the processor, this socket connects an industrial terminal system (cat. no. 1770–T1, –T3).

To connect with any of these terminals, use the program panel interconnect cable (cat. no. 1772–TC). Figure 3.7 shows the programming terminal connections to the communication adapter module.

When an industrial terminal is connected this way, you can perform all terminal functions except cassette loads, or dumps. You must disconnect the KA2 perform these functions.

3-10

Figure 3.7 Industrial

Chapter 3

Module Installation

Terminal Connection

Channel A

Program Panel Interconnect Cable (cat. no. 1772-TC)

10219a-I

Data Highway/Processor Cable Connector

The bottom connector of a 1771–KA2 module is labeled PROCESSOR. The communication module communicates with the station processor through this connector. The Data Highway/Processor cable (cat. no. 1771–CN, –CO, –CR) connects from this socket to a socket on the fact of the station processor. On a PLC–2/20 or PLC–2/30 this is the connector labeled PROGRAM PANEL; on a Mini–PLC–2 or Mini–PLC–2/15, the connector is labeled INTERFACE. (Refer to Figure 3.8) and on a Mini–PLC–2/05 the socket is labeled INTFC.

3-11

Chapter 3

Module Installation

Figure 3.8 Data

Highway/Processor Cable Connection

PLC-2/20 Processor

PLC

2/20

AC FUSE

Connector Labeled

“Program Panel”

Communication Adapter Module (cat.no. 1771-KA2)

Processor Connector

Data Highway Processor Cable (cat.no. 1771-CR)

a. Connection to PLC-2/20 or PLC-2/30 Processor

Mini-PLC-2/15 Module

Connector Labeled “Interface”

b. Connection to Mini-PLC-2, Mini-PLC-2/05, and Mini-PLC-2/15

Data Highway Processor Cable (cat.no. 1771-CN, -CO)

Communication Adapter Module (cat.no. 1771-KA2)

Processor Connector

10865-I

A Second Link

To provide a second communication link at a data highway station, you can connect a KA2 module to another KA2 or to an A–B 1771–KG (series B) interface module to provide an RS–232–C link and a Data Highway link. These links enable communication with, say, a PLC–2 family processor on the highway, and a stand–alone computer.

3-12

In such a scheme, the 1771–KG module can be connected directly to the PLC–2 family processor, and the KA2 connected to the PROGRAM INTERFACE connector of the 1771–KG, or vice versa.

Commands

Chapter

General

The primary function of a KA2 module is to transfer data to and from its station processor. The module is instructed to transfer specific units of data by user-programmed commands. The communication adapter module transmits and receives the following set of non-privileged commands:

Protected write Protected bit write Unprotected write Unprotected bit write Read

These commands are of three general types: write, bit write, and read. (Refer to Figure 4.1). The write and read commands transfer word data between the data table of the local station processor and the data table of a remote station processor. The bit write command controls ON/OFF status of one or more memory bits at a remote station processor.

Figure 4.1 Module

Command Summary

Data Table at Local Station Processor

16-Bit Words

Data Table at Remote Station Processor

Write

Bit Write

Individual Bit

Read

16-Bit Words

Communication Adapter Module

4-1

Chapter 4

Commands

Privileged Commands

This chapter describes functions of these commands and their access to data table locations at station processors. A KA2 module can also receive privileged commands from a computer or another intelligent RS-232-C device through a 1771-KE/KF communication controller module. These privileged commands and their functions (briefly) include:

Diagnostic counters reset - resets to zero all diagnostic timers &

counters in the station interface module.

Diagnostic loop - use to check integrity of transmission over

communication link.

Diagnostic read - reads up to 244 bytes of data from PROM or RAM of

station interface module.

Diagnostic status - reads a block of station information from station

interface module; reply includes station information in module’s data field.

Enter download mode - puts PLC-2 family processor into download

mode. Use before sending physical write commands to station.

Enter upload mode (new on KA2 module) - puts PLC-2 family

processor into upload mode. Use before sending physical reads to station.

Exit download/upload mode - takes PLC-2 family processor out of

upload/download mode. Use to restart processor after uploading or downloading.

Physical read - reads bytes of data from PC data table or program

memory. Use the upload contents of PLC-2 family processor memory to computer.

Physical write - writes bytes of data into PC data table or program

memory. Use to download computer contents to PLC-2 family processor memory.

Set data table size* - sets data table size for PLC-2 family processor.

Use before physical writes on PLC-2 family processor. All PLC-2 family data tables are configurable, but some have wider ranges than others. Check the appropriate manual for the processor in your application.

4-2

Later chapters cover the following:

Command programming (chapter 5) Command status bits (chapter 6) Command initiation and execution monitoring (chapter 7)

Chapter 4

Commands

Terminology: Remote/Local Station

In this and later chapters, we use the terms “remote station” or “local station.” The local station is the point of reference. When describing the commands, for instance, the local station is the one sending the command. A remote station is any station that receives a command from the local station.

Figure 4.1 illustrates this terminology.

Protected/Unprotected

Each 1771-KA2 module command has a prefix, either “protected” or “unprotected.” This prefix denotes memory access of the command. The distinction between these command types is:

Protected commands can access (write into) only specified data table areas. The program in the receiving station processor controls these areas. In that program, a memory access rung determines which data table areas will accept protected write or protected bit write commands. (Rungs are described in chapter 5.) The receiving station ignores protected commands that are not defined by the memory access rung.

Unprotected commands require no memory access rung, and they can read or write into any addressable data table word in the receiving station processor.

The primary distinction between these commands is program restriction of memory access. Switch selections can also be made on the module for write protection, to enable/disable execution of many of these commands. (Chapter 3 gives switch selections.)

Figure 4.2 summarizes the distinction between protected and unprotected commands.

4-3

Chapter 4

Commands

Memory Word Address

Figure 4.2 Protected/Unprotected

Command Distinction

An unprotected command can access any area of data table memeory at a receiving station processor

A protected

021

022 023

End of Data Table

a. Access Definition

command can access only specified

areas (determined by memory access rung in receiving station) of memory

Branch Start Instruction

021 023

G G

10866-I

010

b. Memory Access Branch (typical)

NOTE: For most write and bit write operations between station processors, protected commands should be used. Because memory access must be allowed by the program at the receiving station processor, protected commands allow programmed write protection, which gives the programmer an added degree of control over command execution. Unprotected commands provide the same functions in transferring data, but without this write protection at the receiving station.

Write Commands

4-4

A write command transfers word data from the local station processor to a remote station. A single write command can send from 1 to 121 consecutive data table words.

There are 2 types of write commands that can be sent from a station communication adapter module:

Protected write Unprotected write

The distinction between these types of commands is their memory access. Protected write commands are not executed by the receiving station unless a memory access rung is programmed at that station and switch 1 on write options is set. Because this allows added control over data transfer, use of protected commands is recommended.

Chapter 4

Commands

A write command can control data table words at any station processor. However, certain data table areas at each type of processor have a special function and should not be controlled by write commands. (Sections titled “Accessible Data Table Locations-PLC-2 Processors” and “Accessible Data Table Locations-PLC Processors” cover data table control.)

Bit Write Commands

Bit write commands control the ON/OFF status of bits in a remote station data table. Unlike read or write commands, bit write commands do not transfer data table memory data. Instead, the programmed command rung itself specifies which bits are to be set on or off when the command is executed. (Refer to chapter 5.)

There are 2 types of bit write commands that can be sent from a communication adapter module:

Protected bit write Unprotected bit write

The distinction between these commands is their memory access. Protected bit write commands are not executed by the receiving station unless a memory access rung defining the appropriate memory area is programmed at that station and switch 1 is set. Because this write protection feature allows added control over command execution, use of protected commands is recommended.

A bit write command can control data table areas at any station processor. However, certain data table words at each type of processor have a special function and should not be controlled by bit write commands. (Data table control is the subject of sections titled “Accessible Data Table Locations-PLC-2 Processors” and “Accessible Data Table Locations-PLC Processors”).

On each 1771-KA2 communication adapter module, the sending and receiving of write messages can be enabled or disabled by switch settings. (Refer to chapter 3.)

Bit Write Access

The bit write command can be used to control any accessible data table bit. However, this command must not be used to control the following:

Any bit whose status is controlled by a programmed output instruction. Any bit in a byte that also contains program-controlled bits.

4-5

Chapter 4

Commands

This first restriction simply states that no bit should be directly controlled, that is, addressed, by both an output instruction at its local station processor and a bit write command from some remote station processor.

Bit write commands are generally used to set storage bits in a station processor data table. These storage bits may then be examined in the user program as conditions to energize an output bit. This indirect programming technique allows control using bit write commands, but helps to prevent the confusion that can result if an individual bit is controlled from both an OUTPUT ENERGIZE instruction and a bit write command.

Figure 4.3 gives an example of an indirect programming technique used to control bit 01001, which is addressed by an output instruction, with a bit write command. Here storage bit 12104 is controlled by the bit write command. This bit is then examined by the program to control the status of bit 01001. The output bit, 01001, cannot be directly addressed by the bit write command. However, by controlling the storage bit and examining it in the program, the same effect is achieved.

Figure 4.3 Bit

Control Use (example)

Control of this output desired. However bit

already addressed by

Input

11113

a. Original Rung

Input Output 11113

Storage Bit

12104

Control bit through bit write command to control output 01001.

b. Recommended Technique

output intructions

Output

01001

4-6

Chapter 4

Commands

The second restriction listed above applies when the destination station is a PLC-2 family PC. For these processors, when the station communication adapter module receives a bit write command it manipulates the 8-bit byte of the 16-bit memory word in which the addressed bit is located. (This may be the low byte, containing bits 00-07, or the high byte, containing bits 10-17.) Should program instructions control other bits within the same byte, there is a slight possibility that the communication adapter module may write over programmed status for these program-controlled bits. This would occur only if the program caused a bit to be altered during the time the communication adapter module was executing a received bit write command.

Therefore, when using the bit write command, address only bits within a byte that is set aside exclusively for control by these commands.

Read Command

Accessible Data Table Locations

- PLC-2 Processors

The unprotected read command transfers word data from a remote station processor to the local station data table. A single unprotected read command can access from 1 to 122 consecutive data table words.

The unprotected read command is not restricted by user programming. This command can read data table words from any remote station processor, regardless of either memory access rung programming or module switch settings.

Because this command controls data table words at its local station processor, the rules for data table control apply when using this command. (Data table control is the subject of sections titled “Accessible Data Table Locations-PLC-2 Processors” and “Accessible Data Table Locations-PLC Processor”).

When it executes a read, write, or bit write command, the communication adapter module controls data table locations at a station processor. This section outlines the recommendations for control of data table locations in PLC-2 family processors.

A KA2 module executes read, write, or bit write commands to control any accessible data table words in any of these processors. It also controls user-selected status words in the data table of these processors. (Status words are described in chapter 6.) A KA2 can access most data table words. However, certain memory areas in these processors have special functions that prevent control of these areas by the module. The following are data table areas with a special function in these processors:

4-7

Chapter 4

Commands

Processor work areas Input image table Word 027

Later paragraphs describe the limitations in controlling each of these areas. Access to all other data table areas is subject to the requirements of the programmer.

Processor Work Areas

The processor work areas for PLC-2 family processors are addresses 000-007 and 100-107. These areas are used for specific processor functions and are not accessible to commands from a station communication adapter module. The processor prevents an attempt to write data into this area from a remote station KA2. Note also that an attempt to read data from this area causes all 0’s to be read.

Only privileged commands from a computer can write into or read from this area of the data table.

Input Image Table

The input image table areas for these processors are addressed as follows:

PLC-2 processor: 110-127 PLC-2/30 processor: 110-177 PLC-2/20 processor: 110-177 Mini-PLC-2 processor module: 110-117 Mini-PLC-2/05 processor: 110-117 Mini-PLC-2/15 processor: 110-117

Please see appropriate processor manuals (Table 1.B) for details.

This area of memory is updated each input scan. Any data written into it will be cleared on the next input scan. This limits use of the input image table as a storage area for values or bits. Note, however, that the input image table may be read from or written to another station. This control restriction applies only when attempting to write data into the input image table using a command from a communication adapter module.

4-8

Word 027

Word 027 has a special function with PLC-2 family processors. For example, bits 02710-02717 are used for report generation; bit 02700

Chapter 4

Commands

indicates a low-battery condition. Because of these special functions, care must be exercised in controlling word 027 with a write or bit write command.

The processor does not prevent data from being written to this data table word.

Accessible Data Table Locations

- PLC Processors

When it executes a read, write, or bit write command, the communication adapter module controls data table locations at a station processor. When addressing a command to a Bulletin 1774 PLC processor, note that there are certain data table areas with a special function. These data table areas are not to be used for control by communication adapter module commands:

Any input image table word that has a corresponding input module in a

Bulletin 1778 or 1771 I/O rack Word 377 Word 000

Input Image Table

When an input image table word in the PLC processor data table is unused, that is, has no corresponding input module in an I/O rack, that word can be used for storage. However, should an input module correspond to that word, the data in the word is updated from the input module each I/O scan.

Note that this restriction does not prevent any word of the input image table from being written to another station. This control restriction applies only when attempting to write data into input image table locations.

Word 377

Word 377 has special status functions within the PLC processor. For this reason, the communication adapter module must not execute write or bit write commands into this word.

A read command from a local station can address word 377 at a remote station PLC processor.

4-9

Chapter 4

Commands

Word 000

Reserve word 000 of the PLC processor output image table when using a KA2. This means that commands from another station must not be programmed to control word 000 or any of its bits.

Accessible Data Table Locations

- PLC-3 Processors

Each PLC/PLC-2 station on a Data Highway can read from or write to only one specific buffer file at a PLC-3 station. That is the PLC-3 input file with a number that corresponds to the station number of the PLC/PLC-2 station. For example, the read/write files assigned to PLC/PLC-2 stations 1 to 100 (octal) would be as follows:

PLC/PLC-2

Number (octal)

Station

000 001 I001 002 I002 003 I003 004 I004 005 I005 006 I006 007 I007

010 I010 011 I011 012 I012

. . . . . .

0770 I077

100 I100

Assigned PLC-3 Input File

for Read/W

rite Access

I008

I009 (Not assigned)

4-10

PLC/PLC-2 station numbers are octal, while PLC-3 input files have decimal addresses. This means that PLC-3 input files with an 8 or 9 in their addresses are not used for read/write access by a PLC/PLC-2 station. The only exception to these rules is that station number 000 is assigned input file I008.

Chapter 4

Commands

The PLC/PLC-2 station can use either protected or unprotected commands to access its assigned PLC-3 file. Note, however, that the PLC/PLC-2 station cannot access its assigned file until you create and allocate that file. To create a PLC-3 file, use the CREATE command described in the PLC-3 Programming Manual (publication 1775-6.4.1).

Accessible Data Table Locations

- PLC-4 Microtrol Processors

Programmable controllers can send the following non-privileged commands to a 1773-KA interface module:

unprotected read unprotected write unprotected bit write protected write protected bit write

A 1773-KA module accepts non-privileged commands like other Data Highway interface modules with one exception: the 1773-KA module does not have memory protection rungs. Instead, you set switches that allow or disallow the module to receive protected and unprotected commands.

The PLC-4 Microtrol controller uses a four-digit address for its input, output, flags, store, timer and counter bits. (Timer and Counter status bits require an additional two digits.) When you issue a command from another programmable controller or computer, do not enter these addresses; instead, enter an address code. It is important that you understand these addresses, however, to see how they relate to address codes.

4-11

Chapter 4

Commands

The addressing scheme is summarized in this chart:

able 4.A

Internal

Addressing of a PLC-4 Microtrol Controller

ype of

Address

I=Input 1-8 01-20

O=Output 1-8 01-12

Controller

I.D.

Bit

Address Range

X=Flags 1-8

S=Stores 1-8 01-99

ype of

Address

T = T

imer 1-8 01-32

C = Counter

(1)

Flag bits 31 and 32 have a special significance. See the PLC-4 Microtrol Product Guide (publication 1773-800).

Controller

I.D.

1-8 01-32

Timer/Counter

(1)

01-32

Number

Bit

Description

15 - T

imer Clock 16 - Enable 31 - T

imer T

iming 32 - Done 15 - Count -Down Enable 16 - Count-Up Enable 31 - Overflow Underflow 32 - Done

The memory map for a PLC-4 Microtrol controller, ID #1, shown in Figure 4.4, includes data on inputs, outputs and flags of each active controller on the loop.

4-12

Each member of the PLC-4 Microtrol loop, including the interface module, shares the status of the input, output, and flag bits for each controller on the loop. This becomes significant when you want to determine response time.

Each time you enter a non-privileged command, you must enter an address code. This becomes significant when you want to determine response time.

Figure 4.4 Memory

Chapter 4

Commands

Map for Controller 1

Inputs, Outputs and Flags for each Controller on Loop

Controller 1’s Stores

Controller 1’s Timers/Counters 1–32

Controller 1 Controller 2 Controller 3 Controller 4 Controller 5 Controller 6 Controller 7 Controller 8

S101–S199

Timer/Counter 1

Timer/Counter 32

20 inputs 1101–1120

12 Outputs O101–O112

32 Flags X101–X132

Accumulated

Value

16 15

Preset

Value

32 31

Your Program

Sequencer Tables

Each time you enter a non-privileged command, you must enter an address code. This code designates what part of the controller’s memory the command will affect. Note that this is a code, and not a true memory address. A memory address code is a 3-4 digit code that represents a word (16 bits) in the data table of a PLC-4 Microtrol controller. The right-most digit of an address code represents the controller ID number in octal. For example,

4-13

Chapter 4

Commands

address code 010

addresses the first controller - controller 1 - while

address code 011

addresses the second controller - controller 2.

A PLC-4 Microtrol uses a decimal addressing scheme (Table 4.A). The PLC-2 family of programmable controllers use an octal addressing scheme. Thus, you must convert the PLC-4 Microtrol’s decimal addresses to octal.

Address codes are divided into four sets:

1. store words

2. input, output, and flag words

3. input, output and flag area

4. timer/counter words

When using these address codes, observe these restrictions:

1. Do not address more than one set at a time. For example, if you want

to read both the store and the input words of controller 1, send one command to read the store area, and a second command to read the input words.

2. Do not address more than one controller at a time. For example, if

you want to read the store area of both controller 1 and controller 2, send two separate read commands.

4-14

3. Do not send a command to a controller that is in program mode. A

controller in program mode is not an active member of the loop, because its data table is not being updated.

Chapter 4

Commands

Chapter Summary

This chapter told you about the 1771-KA2’s:

Station terminology Commands, protected and unprotected, reads & writes Processors’ input image table addresses, locations

In chapter 5 you will learn about rungs, codes, and more commands.

4-15

Chapter 4

Commands

4-16

Chapter

Communication Zone Rungs

General

At the beginning of the ladder-diagram program, you enter a special set of rungs that dictate communication adapter module activity. The KA2 scans this set of rungs at power-up for operating information.

WARNING: Do not make on-line edits of the communication zone. Since the module scans the communication zone only when it powers up or when the processor changes state (from program to run), the changes will not affect module operation until you cycle power to the 1771-KA2 module or change the operating mode of the processor. Attempting such edits may cause unexpected communication on the Data Highway.

Communication zone rungs use the standard controller instruction set. However, the meaning of these instructions and addresses differs significantly from their meaning in standard ladder-diagram programming. For this reason, each programmed element in a communication zone rung must be understood as it is described in this chapter, not as it would normally be understood in a ladder- diagram logic context.

In several instances, the 3- or 5-digit number entered above the communication zone rung element has no relation to an actual data table address. This chapter specifically identifies this type of number as either a station number or code. Where one of these designations is given, the actual data table bit or word at that address is not affected by KA2 module operation and may be used in the balance of the user program.

For the purpose of this description, the reference point is termed the local station. All other stations are then considered remote stations. These rungs are entered at the local station so that it can send commands to, or receive commands from a remote station.

Obviously, this reference point is not fixed. Each station - as it is being programmed - is considered the local station at that time.

5-1

Chapter 5

Communication Zone Rungs

Overall Format

The overall format for the communication zone of program is shown in Figure 5.1. This figure shows each type of rung that can be entered in this zone.

The actual communication zone rungs for any station processor may vary significantly from those shown in Figure 5.1. The length of this program area is a function of the number of remote stations processors with which the local station processor communicates and the number of transmissions of data with these remote stations.

Figure 5.1 Communication

Zone Format (general)

Command Rungs

Header Rung

Memory Access Rung

Read/ Write

Bit Write

Delimiter Rung

Start

011

077

[G]

020

[G]

017

[G]

03210 02000 016

03211 01702 12000

Header and delimiter rungs are required for each station processor. Memory access and command rungs are programmed as needed.

015

[G]

070

076

[G]

063

065

[G]

[][]

[G]

[][]

[][][]

12004 12005 12006

12010 12011 13511

017

022

[G]

010

060

[G]

022

024

[G]

12001 12002

[][][]

022

[G]

062

[G]

12003

12007

12600

[]

02707

(

)

OFF

02707

(

02707

(

02707

(

02707

(

)

5-2

Chapter 5

Communication Zone Rungs

The order of these communication zone rungs is as follows:

1. Header rung

2. Memory access rung(s) (as needed)

3. Command rung(s) (as needed)

4. Delimiter rung

These rungs must always appear in this order at the beginning of the ladder diagram program. If you are using two KA2 modules, or a combination of KA2 and -KG modules with the same processor, enter one immediately after the other.

Header Rungs

As a minimum requirement, each station processor must have a header rung and a delimiter rung. This provides the advantage of an ERROR CODE storage word, controlled by the module as a diagnostic indicator.

If you are using two communication modules with the same processor, (possible with 1771-KA2 and 1771-KG series B modules only) you must program a separate and complete communication zone for each module. Modules must have different station numbers.

The figures in this chapter show 3-digit addresses above most GET instructions, but not the 3-digit data value displayed below the GET symbol. This convention is used for clarity, since, for the most part, only the 3-digit GET address is significant when entering a program. In entering communication zone rungs, you needn’t program any data into GET instructions.

A header rung, as shown in Figure 5.2, indicates the beginning of the communication zone. For the communication adapter module (cat. no. 1771-KA2), the output position of this rung is always the LATCH 02707 instruction.

5-3

Chapter 5

Communication Zone Rungs

Figure 5.2 Header

Rung

Local Station Number

Address of Error Code Storage Word

011

[G]

000

Timeout

Preset Code

077

[G] 000 000

015

[G]

02707

(

OFF

)

The 3 GET instructions in the header rung list the following:

Local station number Address of ERROR CODE storage word Timeout preset code

The local station number is a 3-digit number switch-selected on the 1771-KA2 module. This is an octal number from 010 110

to 3768.

to 0778 or from

The ERROR CODE storage word is a status word in the data table of the local station processor, controlled by the communication adapter. (Section titled “Error Code Storage Word,” chapter 6, describes the significance of the ERROR CODE storage word.)

Memory Access Rungs

5-4

The timeout preset code gives a programmed timeout interval for command completion. Based on the 3-digit value entered in the address field of this GET instruction, the communication adapter module monitors command execution for all commands sent from a station. In the examples in this publication, the number 015 is entered as the timeout preset code. This value, which designates a 5-second timeout preset, is suitable for most applications. The significance of this preset code, its computation, and timeout considerations are described in section titled “Timeout Preset Value,” chapter7.

The memory access rung defines data table words that you can access with the following commands:

Protect write Protect bit write

Protected commands, received from a remote station, may control only those local station processor memory areas listed in memory access rungs.

Chapter 5

Communication Zone Rungs

(Note that memory access rungs are not needed to allow unprotected commands; only protected commands require a memory access rung.)

A memory access rung is composed of one or more memory access branches, as shown in Figure 5.3.A. In this format, a BRANCH START precedes a group of 3 GET instructions. The first GET instruction address is the station number of a remote station. The next 2 GET addresses define the word boundaries of the accessible data table area in the local station processor. The specified remote station may control any bit or word within three boundaries through protected commands.

Figure 5.3.B. illustrates the memory area that is now accessible to protected commands from remote station 010, due to the memory access branch of Figure 5.3.A.

Multiple memory access branches can be listed in a single memory access rung. Each group of 3 GET instructions must be preceded by a BRANCH START instruction. (This is true in all cases, even when only one memory access branch is defined.) BRANCH END instructions can be used to fit the memory access rung into the ladder diagram-display format.

Use output instruction, OUTPUT ENERGIZE 02707, to fit the memory access rung into the proper display format. (This output instruction has no significance in memory access rung logic.)

5-5

Chapter 5

Communication Zone Rungs

Figure 5.3 Memory

Access Example

Branch Start Instruction (Required)

Memory Access Boundaries in Local Station Data Table

Remote Station No.

010 020 023

a) Memory Access Branch b) Local Station Processor

Starting Address

GGG

Ending Address

Branch End Instruction (Required)

Area Accessible to Protected Commands From Remote Station No. 010

Data Table

Figure 5.4 shows a memory access rung with multiple branches. This rung lists the remote station that may control specific data table words with protected commands, as follows:

Words 020

023

5-6

Branch Start Instructions Begin Each Branch

020

[G]

000

017

[G]

000

Station no. 020 can control words 070-076 Station no. 017 can control words 063-065 and word 022 Station no. 010 can control words 060-062

As shown in Figure 5.4, a single remote station processor may be identified in more than one memory access rung branch.

Figure 5.4 Memory

070

076

[G]

000

000 000

063

065

[G]

000 000 000 000 000

Access Rung (typical)

017

022

[G]

000 000

010

060

[G]

062

Use Branch End Instructions as Needed

One Branch End Instruction Must Precede Output Instruction

02707

(

)

Chapter 5

Communication Zone Rungs

For practical reasons, do not exceed the display area of the programming terminal when entering these rungs. You can program more than one memory access rung if needed. Note, however, that should multiple memory access rungs be required, you must enter them in succession in the communication zone, immediately following the header rung and before any command rung.

Command Rungs

The command rungs direct the data transfer operations of the communication adapter module. The command rung lists the type of command and the memory areas affected and allows command execution to be initiated in the user program.

There are 2 basic command rung formats that differ only in terms of the unit of memory which they control. The basic command rung formats are:

Word command format Bit command format

Use the word command format for commands that transfer one or more data table words between stations. These are unprotected write, read, and protected write commands.

Use the bit command format for commands that control, from one station, one or more data table bits at another station processor. These are unprotected bit write and protected bit write commands.

In both formats the command rung begins in a similar manner. (Refer to Figure 5.5). The first rung element is an EXAMINE ON instruction, addressing the START bit. The second rung element, termed the command code, tells the remote station number, type, and priority of the command. (Section titled “Message Priority,” chapter 8, describes command priority.) For most commands, normal priority is preferred.

5-7

Chapter 5

Communication Zone Rungs

Figure 5.5 Command

Rung Format

Start

Bit

Command Code

AAAPX

[]

02707 (

REFER TO FIGURES

5.6 AND 5.7

AAA – REMOTE STATION NO.

P – PRIORITY INDICATOR 1 = PRIORITY MESSAGE 0 = NORMAL MESSAGE

X – COMMAND TYPE 0 = PROTECTED WRITE 1 = UNPROTECTED READ 2 = PROTECTED BIT WRITE 3 = UNPROTECTED WRITE 4 = UNPROTECTED BIT WRITE

)[]

After the command code, the command rung then lists the memory areas affected by the command. The format of this area varies, based upon the type of memory area controlled by the command.

5-8

The length of the communication zone in PLC-2 family PCs is limited by the memory available inside the communication module. Very few applications approach this limit, but if you program too many command rungs, the value 26 will appear in the error code word when you place the processor in RUN or RUN/PROGRAM mode.

Each command rung ends with an OUTPUT ENERGIZE 02707 element. This instruction is used solely for the purpose of fitting the command rung into the proper display format. The output instruction of the command rung has no significance in program logic.

Examine START Bit

Each command rung has a unique START bit in a memory word selected by the programmer. (Refer to section titled “START/DONE Word,” chapter 6). The START bits are examined by the communication adapter module. When a START bit is on, the communication adapter module carries out the programmed command.

Chapter 5

Communication Zone Rungs

The START bit is controlled by the program. This allows a command to be initiated only when necessary. (Programming methods for START bit control are given in chapter 7.)

Command Code

The second element in a command rung, the command code, identifies the following:

Remote station number Priority status of the command (priority or normal) Type of command

NOTE: The command code uses the address of an EXAMINE ON instruction, but does not examine or control any bit in the data table of the local station processor.

Start Bit

032

Legend

AAA BBB

CCC

Figure 5.5 shows the coding for this rung element.

Word Command Format

When the command code specifies a protected write, read, or unprotected write command, use the format shown in Figure 5.6.

Figure 5.6 Word

Command Format

Command Code

020

Remote Station Processor Data Table Address

Beginning word address of remote station processor for write/read operation Beginning Word Address of local station processor for write/read operation

Ending Word Address at local station processor for write/read operation

AAA

Local Station Processor Data Table Boundaries

BBB

CCC

027

5-9

Chapter 5

Communication Zone Rungs

This format uses 3 GET statements. The address position of the first GET statement lists a remote station data table word. The specified command operation begins at this memory location. The second and third GET statements define the starting and ending boundaries of the data table words in the local station processor. These words are the beginning and ending data table locations for the words to be transferred in the write or read operation.

In write operations, data words are written to a remote station from the local station data table. For a write command, the first GET element in the command rung lists a beginning address at the remote station. Data is to be written into this word, and succeeding words from the local station data table. The second and third GET elements in this type of rung list starting and ending boundaries for the word or words to be written from the local station data table.

In a read operation, data words are read from a remote station processor into the local station data table. The first GET element in the unprotected read command rung lists the beginning address from which data is to be read. Remote data table words are read in succession, beginning with this address. Words are read only into the area of the local data table bounded by the second and third GET elements in the rung.

Only one set of GET instructions, as shown in Figure 5.6, can be programmed in a single command rung.

Bit Command Format

When the command code specifies a protected bit write or unprotected bit write command, use the format shown in Figure 5.7.

5-10

Figure 5.7 Bit

Command Format

Area May Contain Any Legal Combination Of These Instructions:

Chapter 5

Communication Zone Rungs

Start Bit

Command Code

Branch Start

(If Needed)

HHH

FFFFF

. .

FFFFF

IIIII

Set bit EEEEE in remote station data table on

–] [–

Set bit FFFFF in remote station data table off

–] / [–

GGG

JJJ

027

EEEEE

Legend: EEEEE

This format uses EXAMINE elements that address bits in the remote station processor. These elements control remote station data table bits as follows:

-] [- EXAMINE ON - This rung element instructs the remote station communication adapter module to turn the addressed bit on.

-]/[- EXAMINE OFF - This rung element instructs the remote station communication adapter module to turn the addressed bit off.

Delimiter Rung

Program these elements immediately after the command code. Any combination of these elements may make up this type of command rung. Where necessary, BRANCH START instructions and a BRANCH END instruction can be used to fit these elements into the display area of the programming terminal. For practical reasons, do not exceed this display area. Multiple rungs of this type can be used as necessary.

The delimiter rung ends the communication zone of program. With PLC-2 family processors, this rung always has the format shown in Figure 5.8.

5-11

Chapter 5

Communication Zone Rungs

Figure 5.8 Delimiter

Rung

027

Chapter Summary

Chapter 5 was the RUNG chapter; it discussed:

Communication zone rungs Communication zone of program Header rungs Memory access rungs Command rungs Start bit, command code and word command format Bit command format with EXAMINE ON, EXAMINE OFF elements

In chapter 6 you will read about bit storage, fault words, and error codes.

5-12

Status Words

Chapter

General

A 1771-KA2 communication adapter module controls certain data table words specified in the local station processor by the programmer. These data table words indicate the status of command execution and provide various types of diagnostic information for start-up and troubleshooting. These locations are:

One or more pairs of adjacent words for START/DONE and

REMOTE/LOCAL FAULT bit storage

An ERROR CODE storage word

Refer to Figure 6.1. The programmer specifies the locations of these status words when entering the communication zone rungs, as described in chapter 5. Two START/DONE and REMOTE/LOCAL FAULT bit storage words are defined by selection of the START bit in a command rung. You specify the ERROR CODE storage word in the header rung.

Figure 6.1 Adjacent

Status W

Start Bit

ord

0270703210

G G

Selection of Start Bit Automatically Desig– nates Bits in Two Adjacent Words

Word 032

Word 033

Bits for Command Rung Shown

Command Rung

Start Bits Done Bits

Program Controlled

Remote Fault Bits Local Fault Bits

Start/Done and Remote/Local Fault Words

Communication Adapter Controlled

6-1

Chapter 6

Status Words

Any accessible data table words can be used as status words in the station processor. Note that the same recommendations for data table control given in section titled “Accessible Data Table Locations - PLC-2 Processors,” chapter 4, should be followed when selecting status words. That is, processor work areas, input image table words and word 027 should not be used as status words.

START/DONE Word

The START/DONE word is the first of a pair of adjacent status words for communication adapter module use. This word stores a START bit and corresponding DONE bit for each of up to 8 commands. (NOTE: should more than 8 command rungs be programmed at a station, additional pairs of START/DONE and REMOTE/LOCAL FAULT words can be used.)

The START bit for any command is always in the upper byte (bits 10-17) of the START/DONE word. The DONE bit for this command is then the corresponding bit in the lower byte (bits 00-07) of the same word.

In Figure 6.1.A the sample command rung examines bit 03210 as its START bit. As Figure 6.1.B shows, the corresponding DONE bit is bit

03200. Note that the 5-digit address of START/DONE bits for each command differs only in the fourth digit: the START bit always has a “1” in the fourth digit, the DONE bit always has a “0.”

As its name implies, the START bit initiates command execution. This bit, controlled by the user program, is set ON to initiate the sending of a command. The communication adapter module monitors the status of START bits and executes the corresponding command when its START bit is set ON.

6-2

The DONE bit as its name implies, indicates command completion. This bit, controlled by the KA2, is set ON when a command is executed.

Each command rung examines a unique START bit. Thus, one pair of START/DONE and REMOTE/LOCAL FAULT words has enough bits for up to 8 command rungs. Should more command rungs be programmed, select additional word pairs as necessary.

To optimize memory use and minimize the time required by the communication adapter module to scan START bits, use all 8 START bits in one word pair before using another START/DONE word. For the same reason, when programming communication zone rungs, group in sequential fashion command rungs that use the same START/DONE word.

Chapter 6

Status Words

REMOTE/LOCAL FAULT Word

As Figure 6.1 shows, the selection of a START bit in the program not only causes a corresponding DONE bit to be controlled in the same word, but also causes REMOTE and LOCAL FAULT bits to be controlled in the next data table word. A REMOTE FAULT and LOCAL FAULT bit are controlled for each command. For a command, the position of each of these FAULT bits within their respective bytes corresponds directly to the position of START and DONE bits for that command.

The KA2 controls REMOTE and LOCAL FAULT bits. The module sets a FAULT bit ON when a command cannot be executed due to a hardware-related fault either between stations or between the remote station communication adapter module and its station processor. Figure 6.2 summarizes the significance of these bits.

Figure 6.2 REMOTE/LOCAL FAUL

Processor

PLC

2/20

AC FUSE

T Bit Significance

Local Fault

Possible Sources:

• Disconnected data highway cable

•

Power off at receiving station interface module

•

Unused remote staiton no. address

•

Station interface moduel at local or remote station has disconnected itself as a result of link monitoring

•

Automatic timeout at sending station

Sending Station

Remote Fault

Possible Sources:

•

Remote station processor in program load (or prog) mode

•

Command not executed due to module switch setting at receiving station

•

Fault at remote station processor

•

Power off at remote station processor Disconnected data highway/processor cable

•

Error detected in communication zone of

•

program at remote station proccessor

Processor

PLC 2/20

AC FUSE

Receiving (Remote) Station

10866-I

6-3

Chapter 6

Status Words

REMOTE FAULT bits are in the upper byte of this word. A REMOTE FAULT bit is set ON when a command is received at a remote station but cannot be executed by the remote station. This may mean one of the following:

Remote station processor has detected a fault in its own operation or

has shut down.

Remote station processor has power OFF. Remote station processor has mode select switch in PROGRAM LOAD

(or PROG) mode.

Cable between remote station adapter and processor is disconnected or

faulty.

Module switch setting prevents execution of the received command. Error has been detected in communication zone of program at remote

station processor (PROG indicator may be ON).

A REMOTE FAULT bit indicates that the remote station communication adapter or controller module received a message, but could not communicate with its station processor to execute that command.

LOCAL FAULT bits are in the lower byte of this word, bits 00-07. A LOCAL FAULT bit is set when the local station cannot confirm delivery of the message to the remote station. This may mean one of the following:

Automatic timeout of command completion by communication adapter

module.

Disconnection of the local or remote station interface module from the

Data Highway cable

Loss of power to the remote station communication adapter module Unused station number addressed by the command. Excessive noise along the Data Highway cable caused by other

equipment in the industrial environment.

At the same time it sets a REMOTE or LOCAL FAULT bit ON, the KA2 enters a 2-digit ERROR CODE into the ERROR CODE storage word. (The ERROR CODE storage word is described in the following section.)

6-4

By monitoring these bits in the program, operators can be alerted to hardware conditions that prevent normal transmission and execution of commands. (Programming techniques for monitoring FAULT bits are described in chapter 7.)

Chapter 6

Status Words

Error Code Storage Word

When a command cannot be carried out due to a user programming error or a discrepancy in data handled by the communication adapter module, an ERROR CODE may be written into a data table memory word. The programmer selects the error code storage word and lists it in the header rung of the communication zone of program. This word stores the most recent error code written by the KA2.

Figure 6.3 shows the structure of the ERROR CODE storage word. The lower byte of this word (bits 00-07) stores any ERROR CODE entered by the module. In this byte the ERROR CODE is represented as a 2-digit binary coded decimal (BCD) number from 00-99. Table A.1 (Appendix A) lists and describes these ERROR CODES.

Figure 6.3 ERROR

CODE Word Format

2–Digit Value:

Reference Number

(for codes 01–26)

Counter (for codes 30–99)

Error Codes 00–99

in BCD Format

(Refer to Table 6–A)

17 16 15 14 13 12 11 10 07 06 05 04 03 02 01 00

0–9 0–9 0–9 0–9

ERROR CODES can be grouped as follows:

Codes 01-29 generally indicate that some programming error has been

detected in the communication zone of program. These codes are intended to indicate errors or processor communication faults detected at power-up. The program status indicator (PROG) may be on if one of these codes is displayed.

Codes 30-99 generally indicate that some programming or hardware

related fault has been detected during attempts at communication between stations. Codes 30-99 serve as diagnostic indicators after the initial power-up checks of program have been completed.

A code in this 30-99 group is displayed whenever a REMOTE or LOCAL FAULT bit is set ON.

6-5

Chapter 6

Status Words

The upper byte of the ERROR CODE storage word (bits 10-17) stores a 2-digit BCD value. This value gives supplemental error or fault information, depending on the type of ERROR CODE displayed. It may have one of two meanings:

Reference number Counter

For ERROR CODES 01-29, the upper byte stores a 2-digit reference number. This number points to the location of a programming error within the communication zone of program. This error may be an incorrect instruction or an improper address entered within a rung of the communication zone. In this numbering scheme, the header rung of the communication zone of program is designated as “00.” Subsequent communication zone rungs are numbered sequentially.

Note that ERROR CODES 01-29 are intended as aids in start-up debugging of the communication zone of program. Thus, the reference number stored in this word can be a valuable tool for debugging purposes.

For ERROR CODES 30-99, the upper byte stores a 2-digit counter. This counter shows the number of ERROR CODES 30-99 written into the storage word by the communication adapter module. The counter increments each time a different ERROR CODE storage word.

These codes are generally to be displayed on a programming terminal rather than used in application programming. They have special value in station start-up, when programming errors are detected in the communication zone of program.

By viewing the header rung of the communication zone, the programmer can examine a displayed ERROR CODE and the least significant digit of the counter in this word. (Section titled “Header Rung,” chapter 5, describes a header rung.)

In some instances, however, it may be preferable to display the 2-digit error code using a 7-segment BCD numerical display controlled from output modules of the controller. This 7-segment display, mounted at an operator’s station, can provide a useful troubleshooting aid for quickly locating fault conditions.

6-6

Chapter 6

Status Words

Chapter Summary

This was the WORD and CODE chapter and it discussed:

START/DONE, REMOTE/LOCAL FAULT bit storage REMOTE/LOCAL fault word Error code storage word (Error code list is in Appendix A.)

Chapter 7 continues discussion about command initiation, control bits, fault words, and monitoring.

6-7

Chapter 6

Status Words

6-8

Chapter

Command Initiation, Execution, and Monitoring

General

START/DONE Bit Timing

This chapter describes the support programming for commands at each station processor. This programming uses the START/DONE and REMOTE/LOCAL FAULT bits, described in chapter 6, to initiate and monitor command execution. Using these recommended techniques, the programmer coordinates communication zone programming with his application program.

The START bit that initiates a command is program-controlled; the DONE bit, which indicates command completion, is communication adapter module-controlled. The timing relationship of START and DONE bits is used by the programmer to initiate and terminate commands. The following sections describe this relationship in normal operation and describe the automatic responses that result from faulted operation.

Normal Operation

Command execution begins when the user program turns a START bit ON, normally with a LATCH instruction. The 1771-KA2 communication adapter module detects the ON state of this bit and then begins the operations necessary to format and transmit a command message.

When the remote station communication adapter module receives the command message, it acknowledges it. Then, while normal Data Highway operation continues, the remote station communication adapter module executes the command and prepares a reply message. (A reply message is sent for each type of command.) The remote station communication adapter module responds to a poll for mastership, then transmits its reply message to the local (sending) station. (Refer to chapter 8 for a description of mastership and polling.)

When the local station communication adapter module receives the reply, it sets the done bit on at the local station processor. The DONE bit, in turn, is examined in the user program to turn OFF the START bit.

After the START bit has been turned OFF (unlatched), the communication adapter module resets the DONE bit.

7-1

Chapter 7

Command Initiation, Execution, and Monitoring

ABCD

Figure 7.1 shows the timing of START and DONE bits for a command. The significance of START/DONE bit status is summarized in Table 7.A.

Figure 7.1 START/DONE

Bit T

iming - Normal Operation

Start Bit

Done Bit

On Off

Command/ Response Time

Legend:

Start bit turned on by the program

Done bit set on by the 1771–KA2

communication adapter module to indicate that a command has been completed.

Start bit turned off by the program Done bit set off by the 1771–KA2

communication adapter module after it senses that the start bit has been set off.

able 7.A

ART/DONE Bit Status

Processor Scan

Communication Adapter Scan

7-2

Status Significance

Start

Bit

Done

Bit

0 0 Idle 1 0 1 1 0 1

Command initiated or in progress Command/reply operation complete The processor

, based on the program, acknowledges completion of the command/reply operation (transient condition, since the communication adapter turns the DONE bit OFF in its next scan.)

Chapter 7

ÉÉÉÉ

Command Initiation, Execution, and Monitoring

Faulty Operation

Certain fault conditions can prevent normal reception and execution of commands by the receiving station. To indicate the source of such fault conditions, the KA2 controls REMOTE and LOCAL FAULT bits at the station processor.

In general, the LOCAL FAULT bit indicates that the local station cannot confirm delivery of a command to the remote station. The REMOTE FAULT bit, on the other hand, indicates that the intended receiving station communication adapter module has received the command message, but is unable to execute the command at its station processor. (For a quick summary of the distinction between these FAULT types, refer to Figure

6.3.)

Start Bit

Remote or Local Fault Bit

Done Bit

On Off

The timing relationship of these FAULT bits in command execution is shown in Figure 7.2. In this example, the command initiated at the setting of the START bit executed due to some fault condition. The communication adapter module, detecting this fault condition, sets either a LOCAL or REMOTE FAULT bit.

Figure 7.2 START/FAULT

ABC

Bit T

Command/ Response Time

iming - Faulted Operation

Communication

Adapter Scan

Legend: Start bit turned on by the program

Remote fault or local bit set on

by the communication adapter module to indicate that a fault condition has been detected.

Start bit turned off by program Fault bit turned off by the communication

adapter module after it senses that start bit has been turned off.

7-3

Chapter 7

Command Initiation, Execution, and Monitoring

Recall that the START bit is program-controlled. The REMOTE/LOCAL FAULT bits, meanwhile, are controlled by the 1771-KA2 module. The programmer must keep this relationship in mind when planning START bit control and FAULT bit monitoring in the ladder-diagram program.

Note from Figure 7.2 that the FAULT bit, once ON, remains ON until the START bit is reset (turned OFF). Only after it has detected that the program-controlled START bit is OFF does the communication adapter module then turn the FAULT bit OFF. Note also that the DONE bit is not set ON in the event of a fault condition.

NOTE: In the special case where the START bit is turned OFF by the program before the KA2 sets a DONE or FAULT bit, attempts to send that command are terminated. The LOCAL FAULT bit is pulsed ON for approximately 60 msec in this instance. This type of situation may occur, for example, if some event is programmed to UNLATCH the START bit before command completion.

Controlling The Start Bit

The user program controls the START bit: setting it ON to initiate command execution, turning it OFF after command completion or after a fault is detected. Normally, the START bit is turned ON by a LATCH instruction, OFF by an UNLATCH instruction. The use of retentive LATCH/UNLATCH instructions is best suited for the timing relationship of START, DONE, and FAULT bits and helps to keep programming simple and straightforward.

To LATCH the START bit, the program examines application conditions. These may include input/output device data, values, or other information from the controlled process. For the most part, an application condition used to initiate a command is one of these general types:

The ON or OFF status of some I/O device Transition of some I/O device Timed condition

To UNLATCH the START bit, the program examines the response from the communication adapter module. This response may be one of the following:

DONE bit REMOTE FAULT bit LOCAL FAULT bit

7-4

Chapter 7

Command Initiation, Execution, and Monitoring

Thus, the rung used to UNLATCH the START bit examines these three possible responses in parallel branches of the ladder diagram program.

Section titled “ON/OFF Input Status,” “Transition,” and “Timed” describe the most commonly used forms of START bit control. Each section describes a different method for initiating command execution; all examples show how the program uses both DONE and FAULT bits to UNLATCH the START bit.

An important assumption underlies the examples outlined in sections titled “ON/OFF Input Status,” “Transition,” and “Timed” and shown in Figures 7.3 through 7.5. Here, the program automatically re-tries transmission of a command in the event of a fault. Only the DONE bit terminates attempts at command execution; a LOCAL or REMOTE FAULT bit response causes the program to re-initiate command execution. (This type of programmed re-try is not to be confused with the re-try procedure of the 1771-KA2 module itself; transparent to user programming, the module automatically attempts several re-tries of a message before it sets a FAULT bit. Section titled “Floating Master,” in chapter 8, describes these automatic re-tries of the module.)

Programmed re-try has distinct advantages. As the communication adapter module continuously tries to send the command message, any data content of the message (for a write command) is continuously updated. As soon as the fault condition is corrected, the message is sent, with the latest data. In addition, once the command is completed, the program automatically UNLATCHES the START bit. This eliminates the need for a manual reset of the START bit when a fault condition is corrected.

ON/OFF Input Status

The ON or OFF status of an input device can be used to LATCH the START bit. Figure 7.3 shows rungs for this type of command initiation.

7-5

Chapter 7

Command Initiation, Execution, and Monitoring

Figure 7.3 Status-Initiated

Command

11111

03202

Local Fault 03302

Remote Fault

03312

Remote Fault

03312/03302

InputDone

11111

Local FaultInput

Start

032

Start

032

In this example, the first rung is programmed to LATCH the START bit when the input, bit 11111, is ON, provided that both FAULT bits are OFF. The second rung is programmed to UNLATCH the START bit based on the response of the communication adapter module.

7-6

In normal operation, the START bit is LATCHED by the input 11111; the FAULT bits, initially, are OFF. This causes the command message to be formatted and sent. Then, when the command is completed, the DONE bit is set ON by the communication adapter module. Note that the input bit, 11111, must also be OFF to UNLATCH the START bit in this example. With this arrangement, the command message is sent only once; input 11111 must be turned OFF, then ON again, to execute this command a second time. In normal operation, the START bit, after successful command completion, remains ON until input 11111 goes OFF. (Recall from Figure 7.1 that the communication adapter module holds the DONE bit ON until after the START bit is turned OFF.)

Should a fault condition prevent normal execution, these rungs provide a programmed re-try of the command. A REMOTE or LOCAL FAULT bit resets the START bit in the second rung. In the first rung, the START bit is LATCHED again after the communication adapter module resets the FAULT bit. (As Figure 7.2 shows, the 1771-KA2 module resets a FAULT bit only after the START bit has been turned OFF.)

Chapter 7

Command Initiation, Execution, and Monitoring

Even though the FAULT bits are continually reset with this method, their usefulness must not be overlooked. The section titled “REMOTE/FAULT Bit Monitoring” outlines a useful method to monitor FAULT bits and control an output indicator based on FAULT bit status.

In some applications, it may be useful to send a command continuously between stations. With the example of Figure 7.3, this can be accomplished by eliminating the EXAMINE OFF instruction for input 11111 in the second rung. This would cause the command to be sent continuously as long as input 11111 remains ON.

Transition

The transition of an input device from ON to OFF and from OFF to ON can be used to LATCH the START bit. This allows a command to be sent each time a condition changes state. Figure 7.4 shows example rungs for this type of command initiation.

7-7

Chapter 7

Command Initiation, Execution, and Monitoring

Figure 7.4 Transition-Initiated

Command

Rung 1

Rung 2

Rung 3

Rung 4

CompareInput

01111

Compare

01111

Remote Fault

Local Fault

11111

Input

11111

Input

11111

Transi– tion

02000 03312/03302

Done

03202

Transition 02000

OFF

Compare

01111

Start

03212

L OFF

Start 03212

7-8

Rung 5

Local Fault

03302

Remote Fault

03312

Done

03202

Transition

02000

Chapter 7

Command Initiation, Execution, and Monitoring

In this example, a storage bit, called the “transition” bit, is manipulated to control the sending of the command. This bit is LATCHED whenever a transition of input 11111 is detected, UNLATCHED only when the DONE bit is set ON. A “compare” bit, 01111 in this example, is used to manipulate the transition bit. In rung 2, the compare bit is controlled to match the ON/OFF status of the input. Because the input and the compare bit are programmed to have matching states, both ON or both OFF, the conditions of RUNG 1 can be TRUE only when the input has just changed from ON to OFF or from OFF to ON. Thus rung 1 conditions set up a “one-shot,” TRUE only long enough to LATCH the transition bit. Note that these rung conditions are FALSE as soon as the processor scans rung 2. The order of these rungs is important for this reason.

With the transition bit LATCHED, the START bit, in turn, is LATCHED in rung 3. This initiates the command. In normal operation, the DONE bit UNLATCHES the START bit in rung 4 and then UNLATCHES the transition bit in rung 5. In faulted operation, however, rungs 3 and 4 repeatedly re-try the command in much the same manner as in the example of Figure 7.3.

Timed

The START bit may be LATCHED periodically to send a command at a user-determined time interval. Figure 7.5 shows example rungs for this type of command initiation.

7-9

Chapter 7

Command Initiation, Execution, and Monitoring

Figure 7.5 Timer-Initiated

Command

Done

032

Timed Bit

046

Done

032

Local Fault

033

Remote Fault

033

046

TON

1.0

PR 010 AC 000

Start

032

Start

032

REMOTE/LOCAL FAULT Bit Monitoring

7-10

In this example, timed bit 04615 is used to initiate the command at every preset interval, 10 seconds. This bit is examined to LATCH the START bit. The DONE, LOCAL FAULT, and REMOTE FAULT bit are examined in parallel branches to UNLATCH the START bit.

In normal operation, after the command is executed, the DONE bit is set ON by the communication adapter module. This causes the program to UNLATCH the START bit. The timer then begins timing again once the DONE bit is set OFF. (As Figure 7.1 shows, the DONE bit is reset only after the START bit is reset.)

Note that this programming causes continuous re-try of a command in the event of faulted operation.

When it cannot execute a command, the Communication adapter module sets a REMOTE or LOCAL FAULT bit ON. These bits, in the data table of the station processor, are located in the word immediately following the START/DONE bit word. They indicate not only that a command was not

Chapter 7

Command Initiation, Execution, and Monitoring

executed, but also point to the general type of fault condition that prevented command completion.

The user program must monitor the REMOTE and LOCAL FAULT bits for each command. The recommendations of this section describe two methods for monitoring FAULT bits and using these bits to signal a fault condition.

Diagnostic FAULT Rungs

The purpose of monitoring REMOTE/LOCAL FAULT bits is to control one or more output indicators to signal a fault condition. Fault indicators controlled for this purpose may be as simple as a warning light or an annunciator, or as complex as a line printer or CRT terminal used to display a fault message. By controlling the fault indicator device, the user program can alert user personnel to the nature and location of a fault condition.

To monitor the REMOTE and LOCAL FAULT bits, a programmer must understand their timing relationship to the corresponding START bit. Figure 7.2 summarizes this relationship.

The section titled “Controlling the Start Bit” showed how the FAULT bit can be programmed to UNLATCH the START bit in a fault situation and thus provide automatic re-tries through the program. When used in this manner, however, a FAULT bit will be rapidly cycled ON and OFF if a fault is detected. Because the fault bit can be constantly changing state at a rapid rate, the program must use some method of detecting this transient state of any FAULT bit and of controlling the output device based on this state.

Figure 7.6 shows a simple method for the control of a fault indicator. Here, either the REMOTE or LOCAL FAULT bit can LATCH the output indicator ON. The indicator remains ON until the DONE bit is energized. This then UNLATCHES the output indicator in the second rung of Figure 7.6. This example allows for the transience of the FAULT bits, since the first rung need only be TRUE once for the output indicator to be latched.

7-11

Chapter 7

Command Initiation, Execution, and Monitoring

Figure 7.6 FAULT

Bit Diagnostic Rungs (Single Command Example)

Remote Fault

033

Local Fault

033

Done

03200

Output

Indicator 01000

OFF

Output

Indicator

010

The method of Figure 7.6 can be extended to monitor multiple commands from a station, controlling multiple output indicators as necessary. However, where more than one command is being sent from a station, the use of multiple output indicators may not be practical. In this instance, a single output indicator can be used to signal all REMOTE or LOCAL FAULT conditions for commands from that station. Figure 7.7 shows a method for fault indicator control assuming multiple commands.

7-12

Figure 7.7 FAULT

Bit Diagnostic Rungs (Multiple Commands Example)

Chapter 7

Command Initiation, Execution, and Monitoring

Rung 1

033

Rung 2

033

Rung 3

Local Fault

Remote Fault Status

Rung 4

Timed Bit

Status

055

030

033

Local Fault Status

055

033

033 04/033 03/033 02/033 01/033 00

033 14/033 13/033 12/03311/033 10

Remote Fault Status

055

030

TOF

0.1

PR 020 AC 000

Output

Indicator

010

This example shows the FAULT bit monitoring for 8 commands. The 8 LOCAL FAULT bits are monitored in rung 1. As long as all 8 bits are OFF, status bit 05500 remains ON. However, should any LOCAL FAULT bit be ON, status bit 05500 is de-energized. In rung 2, the 8 REMOTE FAULT bits are monitored in the same manner, to control status bit 05501.

The status bits controlled by rungs 1 and 2 are, in turn, used to control an OFF-DELAY timer in rung 3. The OFF-DELAY timer begins to time when either of the status bits goes from OFF to ON, that is, when rung conditions go from TRUE to FALSE. Bit 03015, the timed bit of the timer, controls the output indicator. As soon as the conditions of the timer in rung 3 are TRUE, this bit is set ON causing the indicator to be energized. Once ON, this bit remains on as long as the timer is timing, that is, for at least as long as the preset interval. In the example of Figure 7.7, this preset is set at 2 seconds. This value is not critical but should exceed 0.5 seconds for practical purposes.

7-13

Chapter 7

Command Initiation, Execution, and Monitoring

The OFF-DELAY timer is useful in this application because it is continually reset when its rung conditions go TRUE. This means that the timed bit, 03015, remains on for as long as any FAULT bit is changing state during programmed re-tries. This keeps the output indicator on until after the DONE bit indicates command completion.

NOTE: Using the rungs of Figure 7.7, the indicator goes ON automatically at power-up, or whenever the mode select switch on the processor is changed from the PROGRAM LOAD (or PROG) mode to any other mode. However, the indicator only remains on initially for the preset interval; after this time, the indicator is valid for fault conditions.

Rungs 1 and 2 examine all 8 FAULT bits of each type. Should fewer than 8 command rungs be programmed at a station processor, fewer bits need be examined. Then, should command rungs be added subsequently, the appropriate bits could be addressed in rungs 1 and 2. Conversely, if more than 8 command rungs were programmed at a station, additional rungs would be needed to examine both REMOTE and LOCAL FAULT bits for the additional commands. Status bits controlled by these additional rungs could then be examined in branches of rung 3, parallel to those shown.

Timeout Preset Value

Of course, other methods can be used to monitor REMOTE and LOCAL FAULT bits. Such factors as availability of output terminals, memory space, and type of application dictate the specifics of FAULT bit monitoring and program response.

Use of FAULT bits in start-up and troubleshooting procedures is described in chapter 9.

In addition to its REMOTE/LOCAL FAULT bit control, a 1771-KA2 module also provides an automatic timer for monitoring command completion. While it functions automatically during module operation, the timer uses a preset value entered in the user program. This feature enables the module to monitor command execution time without using timer (TON) instructions in the user program.

Figure 7.8 shows the significance of the timeout preset interval. From the time the START bit is set ON, the module must set either a DONE bit or a REMOTE or LOCAL FAULT bit within the timeout preset interval. Should the module detect no DONE or FAULT bit response within the preset interval, some type of fault is assumed. As a response to this type of timeout situation, the module sets the LOCAL FAULT bit ON and

7-14

Chapter 7

Command Initiation, Execution, and Monitoring

enters the value 37 in the lower byte of the ERROR CODE storage word of the header rung.

Figure 7.8 Timeout

Preset Significance

Header Rung (Representation)

G G G (L)

Code ”37” Entered if

Timeout Occurs

Start Bit

Done Bit

Remote Fault Bit

Off

Code

QQQ

X37

Timeout Preset Interval, Within this Period Done or Fault Bit Expected

Local Fault Bit

Off

Local Fault Bit Set if Timeout Occurs

Time

7-15

Chapter 7

Command Initiation, Execution, and Monitoring

Timeout preset monitoring is intended as a backup for the other communication monitoring functions of the module. It is designed to signal any condition where the module has not completed its communication with another station or detected some fault condition within a short time. Because this timer is primarily intended as a backup for some LOCAL FAULT type of situation, its preset value is not critical. In the examples in this manual, a nominal value of 5 seconds, coded 015, is programmed as the timeout preset value. This value is appropriate for most applications.

Programming the Preset Code

The timeout preset code for Data Highway communication is entered in the header rung of the communication zone of program. The address field of the third GET instructions in this rung is used for the timeout preset code. Figure 7.8 shows the position of this rung element.

The 3-digit address of a GET instruction is an octal (base 8) number. Because only octal values can be entered in this address field the timeout preset value is a code, computed as outlined in this section.

As section titled “Timeout Preset Value” points out, the timeout preset is not a critical value. For most applications, a 5-second present is acceptable. The code for this timeout preset is 015. However, there may be instance where another timeout preset interval is desired. Table 7.B lists the 3-digit codes for intervals from 1 to 10 seconds. Note that values listed provide nominal values that will vary with activity level in the KA2.

able 7.B

Timeout

Preset Codes

imeout Interval

(Sec,) Code

1 011 2 012 3 013 4 014 5 015 6 016 7 017 8 020 9 021

10 022

7-16

Chapter 7

Command Initiation, Execution, and Monitoring

If it is necessary to use a value other than those provided in Table 7.B, compute the 3-digit timeout preset code as follows:

1. Select a timeout preset interval. This interval must be at least one

second.

For the purpose of computing the code, label this number “S.”

EXAMPLE: desired interval = 7 seconds = S

2. Compute a decimal (base 10) number using the desired interval of

step 1 in the following formula:

S + 8

EXAMPLE: S + 8 = 15

3. Convert this value to a 3-digit octal (base 8) value.

EXAMPLE: 15

= 17

For a brief description of decimal-to octal conversion, refer to chapter 13 of publication 1772-821, Programming and Operations Manual, Mini-PLC-2 Programmable Controller. You can disable the timeout by using the value 010.

User-Programmed Timeout (Optional)

The automatic timeout of a 1771-KA2 communication adapter module has a backup function. This automatic monitoring routine continuously checks module interaction with other Data Highway stations, timing the execution of commands. This automatic timeout does not check module communication with its own station processor. For a backup check on module/processor communication, an optional programmed ON-DELAY timer instruction (TON) can be used.

With proper module/processor communication, the module sets either a DONE bit or a REMOTE or LOCAL FAULT bit as a response to a command. However, in the event of faulted module/processor communication or faulted module operation, a response bit might not be set. Instead, the START bit would remain on in this instance until the fault situation was corrected. Several programming methods can be used

7-17

Chapter 7

Command Initiation, Execution, and Monitoring

to detect such a condition; the simplest of these methods uses an ON-DELAY timer. Figure 7.9 shows typical rungs that can be programmed for this purpose.

Figure 7.9 Typical

User-Programmed T

imeout

Done

032 02

Remote Fault

033

Local Fault

033

060

TON

0.1 PR 100 AC 000

Output

Indicator

01002

Start

032

Timed Bit

060 15

In the first rung of this figure, timer 060 times the interval between the setting of the START bit for a command and the DONE, LOCAL FAULT, or REMOTE FAULT response of the module. If no response is received within the preset interval of this timer, here 10 seconds, a fault may be indicated and bit 06015 set ON. The second rung examines this bit to turn on a warning indicator. Depending on the individual application, this bit could also be used to enable or disable various parts of the program.

7-18

The preset value of this programmed TON instruction is not critical. For this type of backup monitoring, the programmed preset must exceed the timeout preset interval entered as a code in the header rung. (Remember that the automatic timeout of the module gives a LOCAL FAULT response to a command, which would indicate normal module/processor communication, but faulted communication with some other station.)

As with automatic timeout preset monitoring, a user-programmed timeout is useful as a backup to the other monitoring functions of the

Chapter 7

Command Initiation, Execution, and Monitoring

communication adapter module. (REMOTE and LOCAL FAULT bits at other stations indicate the same types of faults that can be detected using a user-programmed timeout.) A programmed timeout would not be necessary for each command from a station. Instead, a single command at each station can be monitored in this manner. Select a command that is sent regularly for this type of monitoring.

There may be other instances where program monitoring of commands is useful. In some cases, a user-programmed timeout may be used to monitor the execution time of critical commands. An application may require that a critical message, such as a priority command, be sent within a certain limited amount of time. A programmed TON instruction can be used for this purpose; here, however, its preset interval will generally be shorter than the interval entered as the timeout preset for the module.

Chapter Summary

This chapter dovetailed with chapter 6. It discussed command initiation, execution, and monitoring and their association with:

START/DONE bit timing Normal operation START/DONE bit status Faulty operation Control of START bit ON/OFF input status Transition of an input device from ON to OFF and OFF to ON Timed start bits Diagnostic FAULT rungs Timeout preset values Programming a preset code Optional user-programmed timeouts

Chapter 8 discusses interfacing a KA2 with other modules on a Data Highway, mastership of the highway and Data Highway computer commands.

7-19

Chapter 7

Command Initiation, Execution, and Monitoring

7-20

Station Interfacing

Chapter

General

To execute commands, a 1771-KA2 communication adapter module at one station interacts with all other stations interface modules on the Data Highway. This chapter describes this interaction of station interface modules.

Because much of this interaction is transparent to user programming, the information given here is largely for background. However, an understanding of station interaction is useful in optimizing use of each individual communication adapter module and of the Data Highway as a whole. Specifically, the information aids in an understanding of the following:

Floating master operation and polling Message types Sequence of messages for command execution Acknowledgements Re-tries of transmitted messages Priority command designation Automatic disconnection of faulted master Commands that can be sent by computer

Floating Master

Central to the interaction of station interface modules is the concept of shared mastership--the floating master. With this arrangement, no single station controls the Data Highway communication link at all times. Instead, each station vies for mastership based on its need to send messages.

The advantage of this arrangement is that Data Highway operation can continue even if one or more stations are unable to maintain communication. Thus, disconnection of a station or a fault at a station processor or communication adapter module does not disable communication between other operating stations. This minimizes the need for redundancy in many applications.

8-1

Chapter 8

Station Interfacing

Mastership

A Data Highway cable links as many as 64 stations. Because this cable has a single pair of wires, only one station can transmit at a time. When a station interface module gains control of this data link to transmit messages, that station has mastership.

When one station interface module is master, all other station interface modules assume a “slave” or receive mode. This enables these stations to receive and acknowledge messages sent to them. The relationship between the master station interface module and all other stations is shown in Figure 8.1.

Figure 8.1 Master

Station Functions

Master Station

All Other Stations

1. Send Command/Reply Messages

Acknowledgment

2. Send Polling Message Sequence

Signal if Ready

12360

8-2

As master, a communication adapter module can send the following types of messages:

Command Reply Polling

Chapter 8

Station Interfacing

The function of both command and reply messages is the transfer of data between stations. As soon as the communication module attains mastership, it sends its command and reply messages (up to a maximum number--16 for the 1771-KA2).

After the module sends its command and reply messages, it transmits a sequence of polling messages. By this sequence, it selects the next station to be master of the Data Highway communication link.

Command Messages

A command message from the master communication adapter module instructs another station interface module to execute a command. In general, a command from a communication adapter module can do one of the following:

Write data table data to another station Write bit status to another station Request data table data from another station through a read command

The command rung, entered in the communication zone of user program, instructs the communication adapter module to format a command message. Once this message is sent, execution of the command begins. (Command types, execution, and programming are described in chapters 4 through 7.)

Each command message causes a reply message to be generated by the receiving station.

Reply Messages

Reply messages are generated by a station in response to command messages that it receives. The reply message indicates whether the command message was received and whether the station interface module has completed the sequence of events required of it for command execution. For commands that write data, the reply message indicates whether the write operation has been completed at the receiving station. For commands that read data the reply message contains the data specified by the command. If the command was not executed successfully, the reply message contains an indication of the error in the STS byte.

8-3

Chapter 8

Station Interfacing

The reply message is an automatic function of communication adapter module operation, transparent to the user program. To send a reply message, a station must have mastership.

Acknowledgement

When a station receives a message addressed to it, whether it is a command or reply message, the receiving station sends an acknowledgement. The acknowledgement is merely a signal that confirms that a message has been received. Transparent to the user program, the acknowledgement is an automatic function of communication adapter module operation.

The acknowledgement serves 2 basic functions: it indicates that the receiving station is operating and has received the message, and it indicates that the received command or reply message is in intelligible format. Should the proper acknowledgment not be received, a fault in the receiving module may be indicated. In this event, the master station communication adapter module re-tries transmission of the message. The communication adapter module attempts several re-tries for a command or reply message. Re-tries are automatic, transparent to the user program.

If re-tries are unsuccessful, a LOCAL FAULT bit may be set ON at the local (sending) station processor. (LOCAL FAULT bits are described in chapter 6.)

Acknowledgements are sent only by a station that is in the receive mode, not the current master station.

Message Priority

Each message transmitted over the Data Highway communication link has one of these priority levels: normal and priority.

These priority levels determine the order in which stations obtain mastership and the order in which messages are transmitted. Priority messages of a given type (either command, reply, or polling) will always be transmitted before normal messages of the same type.

The programmer designates a priority level for each command message. The command code, an element in each command rung, specifies the priority level of the command message. The station that receives a command message automatically establishes the same priority level for its

8-4

Chapter 8

Station Interfacing

corresponding reply message. (The command code is described in chapter 5.)

Priority commands are executed ahead of normal commands throughout the command/reply message cycle. For this reason, a command should be given priority designation only when special handling of specific data is required. Using an excessive number of priority commands defeats the purpose of this feature and could delay or inhibit the transmission of normal messages.

When a station communication adapter module has a priority command or reply message ready for transmission, the module responds to the next priority poll to gain mastership.

Polling

No single station is permanent master of the Data Highway communication link. Each station bids for mastership when it needs to send a message. The station interface module at the current master station conducts a poll to select the next master station. A poll is an orderly, systematic method to determine which stations have messages to send, and to select one of these stations as master.

The mechanics of the polling algorithm are essentially transparent to you. This is because the communication modules handle this automatically. However, the polling algorithm does lead to the following basic rules that you should follow to optimize Data Highway performance:

Number your stations sequentially whenever possible, and Keep the number of high priority messages as low as possible.

Large numbers of high priority messages slow all traffic on the network. In general, you should limit the number of high priority messages to less than 1% of the total traffic on the Data Highway.

Commands From A Computer

A communication adapter module can execute commands from a computer connected through a communication controller module (cat. no. 1771-KE or -KF). The command set of the computer includes the command set of the 1771-KA2 module:

Protected write Protected bit write Unprotected read Unprotected write

8-5

Chapter 8

Station Interfacing

Unprotected bit write

These commands have the same execution sequence and memory access as the same commands from a communication adapter module.

In addition to these commands, the command set from the computer includes the following, which can be executed by a PLC-2 family processor:

Privileged read Privileged write Diagnostic loop Enter download mode Enter upload mode (New for 1771-KA2) Exit upload/download mode Diagnostic read Diagnostic counters reset Set data table size (New for 1771-KA2) Diagnostic Status

Privileged commands give the computer the capability to read from or write into the entire processor memory. This includes both data commands and user program areas. Privileged commands are used chiefly to load programs from a computer to a station processor on the Data Highway.

During program downloading, outputs are held in their last state by the processor. However, at the computer programmer’s option, privileged write commands can also be used to change data table values during a download of program. (Refer to publications 1771-6.5.8 and 1771-6.5.15.)

Diagnostic commands affect only the communication adapter module at a station, not the station processor. These commands access the read/write memory of the communication adapter module. They provide a check of module activity and permit computer control of specific aspects of communication adapter module behavior. A summary of diagnostic commands and their functions is given in Table 8.A.

8-6

Chapter 8

Station Interfacing

able 8.A

T Diagnostic

Diagnostic loop Echoes transmitted data back in reply message Diagnostic read

Diagnostic counters reset

Diagnostic status Allows access to 28 bytes of processor and

Command Summary

Command Function

Copies up to 245 bytes of data from module memory

Resets all diagnostic error counters n the module

module status information

Other commands are available for communication with other processors, but will return an error code if sent to a PLC-2 family processor.

Indications of Upload, Download (Earlier revisions)

If you are using a revision of the 1771-KA2 module before revision D, or a revision of the 1770-T3 terminal before revision G, and are uploading or downloading, the 1770-T3 terminal will:

display a mode select menu and a communication fault message clear all force instructions

(Later Revisions)

When you connect a 1770-T3 terminal (revision G or later) to a 1771-KA2 module (series A, revision D or later) and perform program uploads with the 1770-T3 terminal in the PLC-2 mode, the terminal does the following:

Uploads

1. Displays the prompt:

UPLOAD IN PROGRESS - PLEASE WAIT FOR COMPLETION

2. disables the PLC-2 mode

3. displays the prompt:

UPLOAD COMPLETED - PRESS ANY KEY TO CONTINUE

4. re-enables the PLC-2 mode and forces are maintained after you press

any key

8-7

Chapter 8

Station Interfacing

Downloads

For program downloads with the 1770-T3 terminal in the PLC-2 mode, the terminal:

1. displays the prompt:

DOWNLOAD IN PROGRESS - ALL FORCES CLEARED

2. displays a mode select menu

3. displays the prompt:

DOWNLOAD COMPLETED - ALL FORCES CLEARED

4. displays a mode select menu

When you connect a 1770-T3 terminal (revision G) to a 1771-KA2 module (series A, revision D) and perform program uploads when the 1770-T3 terminal is not in PLC-2 mode, the terminal displays a mode select menu and the following prompts:

1. UPLOAD IN PROGRESS - PLEASE WAIT FOR COMPLETION

2. UPLOAD COMPLETED

If you perform program downloads when the terminal is not in PLC-2 mode, the terminal displays a mode select menu and the following prompts:

1. DOWNLOAD IN PROGRESS - PLEASE WAIT FOR

COMPLETION

2. DOWNLOAD COMPLETED

8-8

Rockwell Automation 1771-KA2 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual