Rockwell Automation 1775-KA User Manual

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AllenBradley

PLC-3 Communication Adapter Module

(Cat. No. 1775-KA)

User Manual

Introduction 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

About This Manual 11 Module Description 14 Specifications 16 Applications 16

Installation 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hardware Programmable Configuration Parameters 219 Backup Configurations 227 Multiple 1775-KA Modules in One PLC-3 233

Installation

Data Highway Communication 31. . . . . . . . . . . . . . . . . . . . . .

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General 31. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Some Terminology 31 Levels of Programming 34 Data Transfers 36

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Addressing Rules and Examples 41. . . . . . . . . . . . . . . . . . . .

General 41. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Number Systems 42 Addresses 43 Symbols 44 PLC-3 Address Specifications 47 PLC/PLC-2 Address Specifications 410 Remote Station Address Specifications 412 Expression 413

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Editing 51. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General 51. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Editing the Message Instruction 51 Allocating Memory 52 Editing Message Procedures 52

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Table of Contentsii

Message Procedure Commands 61. . . . . . . . . . . . . . . . . . . .

General 61. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Assignment Command 62 CREATE Command 65 DELETE Command 65 Execute 66 EXIT Command 66 GOTO Command 67 IF Command 67 ON_ERROR Command 68 STOP Command 69 Functions 69 Comments 611

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Error Reporting 71. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General 71. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Reporting Error Codes 71 Recovery from Errors 71 Error

Monitoring

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72. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Programming Examples 81. . . . . . . . . . . . . . . . . . . . . . . . . . .

General 81. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Individual Commands 81 Message Procedure 84

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Computer to PC Communication 91. . . . . . . . . . . . . . . . . . . .

Introduction to Layered Communication 91. . . . . . . . . . . . . . . . . . . .

Full-Duplex vs Half-Duplex Protocol for the Data Link Layer 95

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Full-Duplex Protocol 101. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General 101. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Definition of Link and Protocol 101 Full-Duplex Protocol 102

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Half-Duplex Protocol 111. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Half-Duplex Protocol 111. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Multidrop Link 111 Transmission Codes 112 Link-Layer Packets 114 Protocol Half-Duplex Protocol Diagrams 1113 Line

Monitoring

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Environment Definition

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117. . . . . . . . . . . . . . . . . . . . . . . . . .

1120. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table of Contents iii

The Network and Application Layer Protocol 121. . . . . . . . . . .

Network Layer 121. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Application Layer 126

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Message Formats A1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction A1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Basic

Command Set PLC-3 Commands A13 Privileged Commands A20

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A8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Error Codes B1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General B1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Local Error Codes B1 Reply Error Codes B1 Remote Error Codes B3 Local and Reply Error Codes B4 Remote Error codes received from the 1771-KE/KF

1771-KA, and 1774-KA Modules B14. . . . . . . . . . . . . . . . . . . . . .

Remote Error Codes Received from the 1773-KA Module B15

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, 1771-KG,

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Diagnostic Counter Block C1. . . . . . . . . . . . . . . . . . . . . . . . .

Data Highway Port Counters C1. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Modem Port Counters C2

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Detailed Flowcharts D1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Overview D1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

UART Sharing D10 SLEEP and WAKEUP D17 POWERUP D18

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Introduction

Chapter

General

About This Manual

The PLC–3 Communication Adapter Module (cat. no. 1775–KA) is an optional module used in the PLC–3 main chassis or expander chassis. It serves two purposes:

1. Interfacing the PLC–3 processor with the Allen–Bradley Data

Highway

2. Interfacing the PLC–3 processor with an intelligent RS–232–C

device

This manual describes the installation, programming, and operation of the 1775– KA module. This manual assumes that you are already thoroughly familiar with the programming and operation of the PLC–3 processor. It does not assume that you have any prior knowledge of the Allen–Bradley Data Highway.

Organization

The remaining chapters of this manual are organized as follows:

Chapter 2 – describes installation of the 1775–KA module. Chapter 3 – presents concepts and terminology for operating the

1775–KA module on the Data Highway.

Chapter 4 – presents general rules for specifying the data addresses you

use in message procedures.

Chapter 5 – explains how you create and edit message procedures and

commands for the 1775–KA module.

Chapter 6 – describes the command language you use in programming

message procedures.

Chapter 7 – describes how the 1775–KA module detects and reports

various types of errors.

Chapter 8 – presents detailed examples of 1775–KA module commands

and message procedures.

Chapter 9 – introduces a layered approach to writing a driver to enable

a computer to communicate to the 1775–K’s RS–232–C channel.

11

Chapter 1

Introduction

Chapter 10 – describes how to write a full–duplex line driver to enable

a computer to communicate to the 1775–KA’s RS–232–C channel.

Chapter 11 – describes how to write a half duplex line driver to enable

a computer to communicate to the 1775–KA’s RS–232–C channel.

Chapter 12 – describes the network and application layers of a software

driver to enable a computer to communicate to the 1775–KA’s

RS–232–C channel. Appendix A – shows detailed message formats. Appendix B – lists error codes reported by the 1775–KA, 1771–KA,

1771–KG, 1771– KE/KF, 1773–KA, and 1774–KA modules. Appendix C – lists diagnostic counters stored at the 1775–KA,

1771–KA, 1771–KG, 1771–KE/KF, 1773–KA and 1774–KA modules. Appendix D – gives detailed flow charts of an example of software

logic for implementing a full–duplex protocol.

Module Description

Figure 1.1 illustrates the front of the 1775–KA module. The module has the following hardware features:

Self–test diagnostic indicators Thumbwheel switch for setting identification number Two ports– one for Data Highway and one for RS–232–C

communication Two sets of indicators – one for each port Switches for selecting fault responses and communication option

14

Chapter 1

Introduction

Figure 1.1 Communication

PASS FAIL

COMMUNICATION ADAPTER

Adapter Module (Cat. No. 1775-KA)

XMTG RCVG ERR DIS

MODEM

INTERFACE

XMTG RCVG RDY ERR DIS

DATA

HWY

SELF TEST

Self–Test Indicators

Thumbwheel Switch

RS–232–C port Indicators

Data Highway Port Indicators

RS–232–C Port

Data Highway Port

DATA

HWY

10000-I

In addition, the module provides the following software features:

Programmable configuration parameters Command language that allows for complex logic decisions, looping,

and nesting Symbolic representation of data and addresses Embedded arithmetic expressions and logic operations Decimal, octal, or BCD (binary coded decimal) data entry

15

Chapter 1

Introduction

Specifications

Function

Interface the PLC-3 Processor with the Allen-Bradley Data Highway and/or with an RS-232-C device

Location

Single slot in PLC-3 main chassis or expander chassis

Communication Ports

Data Highway

RS-232-C Modem

Applications

Table 1.C lists the specifications for the 1775–KA module.

Table 1.C

Specifications

Module

Communication Rate

o Data Highway - 57.6 kilobaud

recommended

o modem-programmable from 1

T baud to 19.2 kilobaud

Cabling

o Data Highway-Data Highway

T dropline cable (Cat.no.1770-CD or equivalent

o modem-Modem interface cable

(cat. no. 1775-CKA or equivalent)

Backplane Power Requirement

2.5A max. @ +5V DC

Ambient T

Humidity Rating

emperature Rating

00 o 600C (operational)

-40

850C (storage)

5% to 95% (without condensation)

As already mentioned, the 1775–KA module serves two main purposes:

Interfacing the PLC–3 processor with the Allen–Bradley Data Highway Interfacing the PLC–3 processor with an intelligent RS–232–C device

You can use the module for both of these purposes simultaneously.

In Data Highway applications, the module serves as an interface between the PLC–3 programmable controller and the Allen–Bradley Data Highway. The Data Highway is an industrial communication network that links together as many as 64 distinct stations. Each station can consist of a programmable controller (such as the PLC–3), a computer, or an intelligent RS–232–C device. The central trunkline of the Data Highway may be up to 10,000 feet long, and each station may be as far as 100 feet from the trunkline. Figure 1.2 gives an example of a Data Highway configuration.

16

Chapter 1

Introduction

Figure 1.2 Example

PLC-3

Controller

1775-KA

Data Highway Configuration

Allen-Bradley Data Highway

Module

NOTE: All PCs are Allen-Bradley

Up to 64 Stations

10001–I

17

Chapter 1

Introduction

The PLC–3 can support multiple 1775–KA modules in the same PLC–3 chassis. This provides the PLC–3 with concurrent access to several independent Data Highways.

The 1775–KA module can also serve as an interface between the PLC–3 programmable controller and an intelligent RS–232–C compatible device or any Allen–Bradley PC and its Data Highway module. Some examples of this application of the module are the following:

Interfacing two PLC–3 controllers through a modem link Interfacing a PLC–3 controller with a computer (either directly or

through modems) Interfacing a PLC–3 controller with a remote Data Highway through a

modem link Interfacing a PLC–3 controller as a slave station on a multipoint

modem link Interfacing a PLC–3 controller on a point–to–point link with PLC–2

Family processor through a 1771–KG module (The 1772–LR processor

is not supported in this configuration.)

Figure 1.3 shows the 1775–KA module in a typical modem application.

Figure 1.3

Modem Application

Typical

PLC-3

Controller

Modem

Computer

1775-KA

NOTE: Modems required only for distances greater than 50 feet.

Module

Modem

10002–I

18

Installation

Chapter

General

Hardware Installation

This chapter describes installation of the 1775–KA module in two phases:

Installing hardware Programming configuration parameters through the PLC–3 LIST

function

Please read the entire manual carefully before attempting to install the module.

For best results when installing the 1775–KA module, proceed in the order indicated below.

Switch Settings

The 1775–KA module has a number of hardware switches that must be set before the module can be installed in the PLC–3 processor. There is a thumbwheel switch on the front edge of the module and a group of option switches on the bottom edge.

Thumbwheel Switch

Figure 2.1 shows a thumbwheel switch on the front edge of the 1775–KA module. This thumbwheel switch designates the number used by the PLC–3 processor to distinguish one 1775–KA module from another. Rotate the thumbwheel to select the desired identification number.

21

Chapter 2

Installation

Figure 2.1

iew of 1775-KA Module

Front

PASS FAIL

XMTG RCVG ERR DIS

COMMUNICATION ADAPTER

XMTG RCVG RDY ERR DIS

MODEM

INTERFACE

DATA HWY

SELF TEST

Self–Test Indicators

Thumbwheel Switch

RS–232–C port Indicators

Data Highway Port Indicators

RS–232–C Port

22

Data Highway Port

DATA

HWY

If there is only one 1775–KA module in the PLC–3 chassis, set its thumbwheel switch to the number 1. If there are multiple 1775–KA modules in the same PLC–3 chassis, set their thumbwheel switches to consecutive numbers, starting with the number 1. You may write the selected number in the space provided beside the thumbwheel switch.

10003-I

Chapter 2

Installation

CAUTION: To guard against unpredictable operation of the PLC–3 processor, do not change the setting on any thumbwheel switch while the 1775–KA module is powered–up.

Option Switches

Figure 2.2 shows a set of four option switches on the bottom edge of the 1775– KA module. Switches 1 and 2 are used when the PLC–3 controller is programmed to operate in a backup configuration. Switch number 1 determines whether or not a fault in the 1775–KA module will cause the primary PLC–3 controller to switch over to the backup PLC–3. Switch number 2 determines whether or not the 1775–KA module will disable its Data Highway port when the PLC–3 becomes deactive. Switch 3 is for RS–232–C communication. Switch 4 is reserved for future use and should always be left open (up, or off). Use Table 2.A below to determine the appropriate switch setting:

Figure 2.2 Option

Switches

23

Chapter 2

Installation

Table 2.A 1775-KA Switch Settings

If this

switch: Is: Then

1 OPEN

1 CLOSED

2 OPEN

2 CLOSED

the PLC will switch over to backup whenever one of the following fault conditions occurs:

1. The 1775-KA module tries to hold control of the PLC-3 backplane for more than 138 microseconds.

The 1775-KA module experiences a execution timeout of more than 32 milliseconds

The 1775-KA module experiences an internal stack

overflow

The 1775-KA module experiences severe Data Highway communication problems.

the primary PLC-3 will not switch to backup when a fault occurs with the 1775-KA module.

the 1775-KA module will disable is Data Highway port whenever the primary PLC-3 controller becomes deactive. The module will no longer be able to transmit or receivemessages through its Data Highway port.

Also, setting switch 2 to open enables the backup operation feature.

the Data Highway port on the module will remain active if the primary PLC-3 becomes deactive.

24

3 OPEN

3 CLOSED

4 OPEN

the module may be connected up to 7,000 cable feet away from a 1771-KF In addition to setting switch 3 to the open position, you must also set switch 2 to closed position. This makes pin 25 on the RS-232-C port of the 1775-KA module active (refer to figures

2.8 to 2.10). Note that switch 3 must always be closed for

communication with an RS-232-C device other than a 1771-KF

the MODEM INTERF connected to a standard RS-232-C device that is located within 50 cable feet of the module.

Switch 4 is reserved for future use and should always be left open.

, a 1771-KG, 1773-KA or another 1775-KA module.

, 1771-KG, 1773-KA, or 1775-KA module.

ACE port of the 1775-KA module may be

Module Placement

After setting the thumbwheel switch, insert the module into any one of the module slots in the PLC–3 processor chassis. Whenever you power–up the processor, the module will receive power also.

Chapter 2

Installation

Indicators

There are three sets of LED indicators on the front of the 1775–KA module (Figure 2.1). The first group, labeled SELF–TEST, indicates the result of internal diagnostic tests that the module continuously performs on its own hardware and firmware. The second group, labeled MODEM INTERFACE, indicates the status of communication through the module’s RS–232–C port. The last group, labeled DATA HWY, indicates the status of communication through the module’s Data Highway port.

Table 2.B. tells what each indicator means.

Table 2.B

Indicators

LED

Indicator

Group

Self-Test PASS

Modem

Interface

Data

Highway

Indicator

Label

FAIL

XMTG

RCVG

ERR

DIS

XMTG

RCVG

RDY

ERR

DIS

Normal

State

OFF

ON or

OFF

Meaning When ON

Module has passed its own internal diagnostic test

Module has failed its own internal diagnostic tests

Module is transmitting a message over the modem interface port

Module is receiving a message over the modem interface port.

User programming error

Module is disabled due to a fault in the PLC-3 processor, or modem interface port is disabled through the LIST function

Module is transmitting a message over the Data Highway port

Module is receiving a message over the Data Highway port

[1]

Module is ready to transmit a message over the Data Highway port and is waiting to acquire mastership of the highway

User programming error or communication error on either the Data Highway or the Modem port

Module is disabled due to a fault in the PLC-3 processor is disabled through the LIST function

, or Data Highway port

[1]

Depends

on amount of data highway activity

25

Chapter 2

Installation

Data Highway Cable Connections

There are two cable connectors, or ports, on the front of the 1775–KA module (Figure 2.1). The bottom port, labeled DATA HWY., is for connection to the Allen–Bradley Data Highway. If you are using the 1775–KA module in a Data Highway application, plug the Data Highway dropline cable into this port. For details on the installation of the Data Highway cable, refer to the Data Highway Cable Assembly and Installation Manual (publication 1770–810).

RS-232-C Cable Connections

The RS–232–C port, labeled MODEM INTERFACE on the 1775–KA module, can interface with any RS–232–C device that is capable of understanding and generating the communication protocol described in this chapter. Some typical RS–232–C applications are:

Interfacing two PLC–3 controllers through a modem link (Figure 2.3)

Figure 2.3

Two PLC-3 Controllers

Linking

PLC-3 Controller

Modem

1775-KA

PLC-3 Controller

Module

Modem

26

1775-KA

Module

NOTE: Modems required only for distances greater than 50 feet.

10004–I

Chapter 2

Installation

Interfacing a PLC–3 controller with a computer, either directly or

through modems (Figure 2.4)

Figure 2.4

a PLC-3 Station to a Computer

Linking

PLC-3

Controller

Modem

Computer

1775-KA

Module

Modem

10005–I

27

Chapter 2

Installation

PLC-3

Controller

Interfacing a PLC–3 controller with a remote Data Highway through a

modem link (Figure 2.5)

Figure 2.5

a PLC-3 Station to a Remote Data Highway

Linking

Modem

1775-KA

NOTE: All PCs are Allen-Bradley

Module

Modem

1771-KF Module

Allen-Bradley Data Highway

28

Up to 64 Stations

10006–I

Interfacing a PLC–3 controller to a PLC–2 Family processor through a

1771–KG module in a point–to–point link (Figure 2.6)

Figure 2.6

a PLC-3 to PLC-2 Family Controller

Linking

PLC–3 Controller

Chapter 2

Installation

Modem

PLC–2 Controller

1775–KA

1771–KG Module

Module

Modem

NOTE: Modems required only for distances greater than 50 feet.

10007-I

29

Chapter 2

Installation

Computer

Master Station

Interfacing a PLC–3 controller as a slave station on a multipoint

modem link (Figure 2.7)

Figure 2.7

a PLC-3 to a Multi-drop Modem Link

Linking

Multidrop Modem

Multidrop Modem Link

The first four applications above use the module’s RS–232–C port in the unpolled mode, while the last application uses the polled mode. You can select the mode of operation and other characteristics of the RS–232–C port through the LIST function.

Slave Stations

PLC-3 Controller

1775-KA

Modem

Module

10008–I

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Each mode of operation requires a different communication protocol. The unpolled mode uses full–duplex protocol (chapter 10) while the polled mode uses half–duplex protocol (chapter 11). In general, full–duplex protocol gives faster data throughput but is more difficult to implement; half–duplex protocol is easier to implement but gives slow data throughput.

NOTE: In other Data Highway documentation, full–duplex protocol might be referred to as DFI protocol, and half–duplex protocol might be referred to as polled–mode protocol.

Hardware Interface

The modem interface is based on EIA RS–232–C and related standards. This interface should be compatible with most dedicated and dial–up network RS–232 modems.

Mechanical

The RS–232 connector on the 1775–KA module is a 25–pin male connector.

Electrical

Input and output levels on the RS–232 connector conform to the RS–232–C standard. The transmitter has increased capability to drive a 7,000 foot isolated lines. This number depends on baud rate and refers to only direct wire connections. (Refer to Table 2.C.)

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Table 2.C Distance

Rate V

ariations

Distance

in feet

1,000 19,200

2,000 9,600

3,000 9,600

4,000 4,800

5,000 4,800

6,000 2,400

7,000 2,400

Maximum

Baud Rate

The receiver is designed to sense the signal generated by a similar transmitter, and is electrically isolated from all other circuitry on the module. It consists of an opto–isolater circuit with an input and return connection at the RS–232 connector. All other signals on the RS–232 connector are driven and received by standard RS–232 interface circuits, and have a maximum drive capability of 50 feet.

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Pinout

The necessary RS–232–C port connections are described in Table 2.D below:

Table 2.D RS-232-C

Port Connections

Signal at the

1775-KA Abbreviation Pin Input/Output

chassis/shield drain

transmitted data

received data

request to send

clear to send

data set ready

transmitted data return

data carrier detect

data terminal ready

received data return

TXD 2 Output

RXD 3 Input

RTS 4 Output

CTS 5 Input

DSR 6 Input

TXDRET 7/14

DCD 8 Input

DTR 20/11 Output

RXDRET 25/13

TXD (transmitted data) caries serialized data. It is output from the

RS–232 connector.

RXD (received data) is serialized data input to the RS–232 connector.

RXD and RXDRET are isolated from the rest of the circuitry on the module.

RTS (request to send) is a request from the RS–232 connector to the

modem to prepare to transmit. It typically turns the data carrier on. When you select the full duplex mode RTS is always asserted. When you select the half duplex mode RTS is turned on when the module has permission to transmit; otherwise it is off.

CTS (clear to send) is a signal from the modem to the RS–232

connector that the carrier is stable and the modem is ready to transmit. The module will not transmit until CTS is true. If CTS is turned off during transmission, the module will stop sending until CTS is restored.

DTR (data terminal ready) is a signal from the RS–232 connector to the

modem to connect to the phone line (that is, “pick up the phone”). The module will assert DTR all the time except during the phone hangup

213

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Installation

sequence. Some modem will not respond to DTR until the phone rings, while others will always pick up the phone whether it is ringing or not.

DSR (data set ready) is a signal from the modem to the RS–232

connector that the phone is off–hook. (It is the modem’s answer to DTR). The module will not transmit or receive unless DSR is true. If the modem does not properly control DSR, or if no modem is used, DSR must be jumpered to an RS–232 high signal at the RS–232 connector. (It can be jumpered to DTR).

DCD (data clear ready) is a signal from the modem to the RS–232

connector that the carrier from another modem is being sensed on the phone line. It will not be asserted unless the phone is off–hook. Data will not be received at the RS– 232 connector unless DCD is true. In the full duplex mode the module will not transmit unless DCD is true. If the modem does not properly control DCD, or if a modem is not being used, DCD must be jumpered to DTR at the RS–232 connector.

TXDRET (transmitted data return) is the return signal for TXD. It is

connected to module logic ground through a resistor.

RXDRET (received data return) is the return signal for RXD. It is

connected to the isolated receiver, and is isolated from all other circuitry on the module.

Connections To The RS–232 Port

Connection to the RS–232 port of the 1775–KA can be one of two types:

Short line (50 feet or less) Isolated long line (between 50 and 7,000 feet)

For short lines, the connection may be either direct or through modems.

You connect an intelligent, RS–232–C compatible device to an interface module by attaching a cable to both the device and to the module socket labeled RS– 232–C CHANNEL. The RS–232–C device may be another Allen–Bradley communication interface module or another manufacturer’s device. For a standard RS–232–C connection, the cable should be no longer than 50 feet. If your RS–232–C device has an Allen–Bradley line driver/receiver, you may use a cable up to 7,000 feet long.

If you want to connect the 1775–KA module to a 1771–KG or 1771–KE/KF module through the RS–232–C channel, use the cabling pinout diagram (Figure 2.8) to construct your own cable.

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Installation

RS–232–C CHANNEL Connector of 1775–KA Module

1 2

Figure 2.8 Connection

1 2

7 3

5 6 8

to Allen-Bradley 1771-KG or 1771-KE/KF Module

Connect the Shield at One End Only

1 3

RS–232–C CHANNEL Connector

5 6 8

of 1771–KG or 1771–KE/KF Module

Conductors 2 and 7, 3 and 25 must be twisted pairs for distances longer than 50 feet.

Set switch 3 (on the 1775–KA) OFF when the module is communicating with another Allen-Bradley device.

If you want to connect the 1775–KA module to a 1775–KA module through the RS– 232–C channel, use the cabling pinout diagram (Figure 2.9) to construct your own cable.

10009–I

215

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RS–232–C CHANNEL Connector of 1775–KA Module

Figure 2.9 Connection

7 3

5 6 8

Conductors 2 and 7, 3 and 25 must be twisted pairs for distances longer than 50 feet.

Set switch 3 (on the 1775–KA) OFF when the module is communicating with another Allen-Bradley device.

to Allen-Bradley 1775-KA Module

Connect the Shield at One End Only

1 3

RS–232–C CHANNEL Connector

5 6 8

of 1771–KA Module

10010–I

216

If you want to connect the 1775–KA module to a modem or computer, use the cabling pinout diagram (Figure 2.10) to construct your own cable.

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Installation

Figure 2.10 Connection

RS–232–C CHANNEL Connector of

1775–KA

Protective Ground Transmitted Data Received Data Request to Send Clear to Send Data Set Ready Signal Ground

Line Signal Detect Data Terminal Ready

Received Data Return

Module

to user-Supplied Modem or RS-232-C Device

1 2 3 4 5 6 7 8

Set Switch 3 ON to ground pin 25.

User–supplied Moderm or RS–232–C Device

10011–I

Private lines are permanently connected phone lines used with modems. Dialup is not needed. Usually the modem hold the handshake lines in the proper states.

The RS–232 port can be connected to standard American dial–up modems and some European modems. Other European standards specify that the DTR signal will cause the modem to answer the phone whether it is ringing or not, causing the phone to always be “busy”. Since the modem port asserts DTR while waiting for a call, it cannot be used with such modems.

The types of dial–up network modems that can be used are classified into the following types:

Manual: these are typically acoustically coupled modems. The

connection is established by human operators at both ends, who then insert the handset into couplers to connect the computers.

DTE–controlled answer: these unattended modems are directly

connected to the phone lines. A module controls the modem via the

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DTR, DSR, and DCD signals. It incorporates timeouts and tests to properly operate these types of modems.

Auto–answer: these modems have self–contained timeouts and tests,

and can answer and hangup the phone automatically.

The modem port has no means to control an auto–dial modem, although it is possible that it can be used in conjunction with a separate auto–dialer.

Answering

The module continually asserts DTR when it is waiting for a call. Under this condition the modem will answer a call and assert DSR as soon as ringing is detected. The module does not monitor the RING indicator in the RS–232 interface. Once DSR is detected the module starts a timer (around 10 seconds) and waits for the DCD signal. When DCD is detected communication can start.

If DCD is not detected within the timeout, the module turns DTR off. This causes the modem to hangup and break the connection. When the hangup is complete the modem drops the DSR line. This causes the module to reassert the DTR line and wait for another call. This feature protects access to the phone if someone calling a wrong number reaches this station.

Once DCD is detected the module continues to monitor the DCD line. If DCD goes false the timeout is restarted. If DCD is not restored within the timeout, the hangup sequence is initiated. This feature allows the remote station to re–dial in the event the connection is lost by the phone network.

Note that this handshaking is necessary to guarantee access to the phone line. If this handshaking protocol is defeated by improper selection of modem options, or jumpers at the connectors, the modem may answer a call, but if the connection is lost the modem will not hangup. It will be impossible for the remote station to reestablish the connection because it will get a busy signal.

Character Transmission

218

Data is sent serially over the RS–232 interface, one eight–bit byte at a time. The transmission format conforms to ANSI X3.16, CCITT V.4, and ISO 1177, with the exception that the parity bit is retained while extending the data length to eight bits.

Chapter 2

Installation

The transmission format may be summarized as follows:

start bit data bit 0 data bit 1 data bit 2 data bit 3 data bit 4 data bit 5 data bit 6 data bit 7 even parity bit (optional) one stop bit

The 1775–KA module selects baud and parity through the LIST function (section titled Programmable Configuration Parameters).

Programmable Configuration Parameters

A number of installation parameters for the 1775–KA module can be programmed through the PLC–3 LIST function.

The LIST function words by presenting you with a series of lists, or menus, that allows you to select and establish the module’s operating parameters. Each option in an upper–level menu represents a submenu of more detailed options. This process continues until you have selected enough options to define a single parameter in full detail. Figure 2.11 illustrates the menu structure of LIST. To return to the preceding (next highest) level of LIST, press the ENTER key without making a new entry.

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Figure 2.11

Menu for 1775-KA Module

LIST

System Mode 1

Test–Monitor 2 Run Monitor 3 Program Load 4 Remote Enable 5 System Status 6 *Module Status Enter Next >

Modules 1 01

1775–ME8 1775–ME8

2 02 3 03

1775–L3

4 04

1775–S4A

5 05

1775–KA A/E

6 06

1775–LX

7 07

1775–LX

8 08

1775–S4B B/A

9 09

1775–S4B B/A

ENTER NEXT

A/A A/A

A/A

B/A

A/A A/A

Data Hwy Comm Adapter – 01 Chassis 0 Slot 0 1 Module Options 2 Data Highway Port 3 Modem Port Enter Next >

KA–01 Module Options 1

Timeout

2 *Send Unprotected 3

Accept Upload/Download

Accept W

5 Backup Operation 6 PLC–2 Mask

ENTER NEXT

KA–01 Data Highway Port 1 Enable/Disable Port 2 Station Number 3 Baud Rate Enter Next >

rites

KA–01 Module Options

Timeout

Enter Timeout >

KA–01 Data Highway Port Enable

1 Enable 2 *Disable

Enter Next >

KA–01 Data Highway Port

Station Number

Enter Station Number >

KA–01 Data Highway Port Baud Rate

1 38400 2 *57600

Enter Next >

= 50/10 sec

= 377

220

KA–01 Modem Port 1 Enable/Disable Port 2 Station Number 3 Baud Rate 4 Communication Mode

5 Even Parity 6 *Send Embedded

Responses

Enter Next >

oggle selection – select this number to enable

or disable the option.

NOTE: Those selections shown in bold type affect the operation of the module; the LIST

display shows an asterisk (*) to indicate when an option is enabled.

The selections not shown in bold type only cause a movement to another level of LIST

This selections indicated in this figure are

selected by default at the initial power–up.

KA–01 Modem Port Enable

1 Enable 2 *Disable

Enter Next >

KA–01 Modem Port

Station – 377

Enter Station Number >

KA–01 Modem Port Baud Rate

1 1

10 2 300 3 600 4 *1200 5 2400 6 4800 7 9600 8 19200

Enter Next >

KA–01 Modem Port Communication Mode

1 *Unpolled Mode 2 Polled – Subscriber Mode

Enter Next >

10012–I

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Installation

You access the LIST function by typing the word LIST and press the ENTER key. After accessing the LIST function, select option 6 MODULE STATUS from the SYSTEM–MODE MENU. LIST then presents you with a menu that describes the modules in your system. The menu varies according to the modules in your PLC–3. A typical menu might be:

MODULES: 1 01 1775–ME8 A/A 2 02 1775–ME8 A/A 3 03 1775–L3 A/A 4 04 1775–S4A B/A 5 05 1775–KA A/E 6 06 1775–LX A/A 7 07 1775–LX A/A 8 08 1775–S4B B/A 9 09 1775–S4B B/A ENTER NEXT<

Under MODULE STATUS, select the option for 1775–KA. At this point, LIST presents you with the following menu for the 1775–KA module:

DATA HWY COMM. ADAPTER–nn CHASSIS cc SLOT ss 1 MODULE OPTIONS 2 DATA HIGHWAY PORT 3 MODEM PORT ENTER NEXT>

In the above and all following menus, “nn” represents the thumbwheel setting of the 1775–KA module, “cc” represents the chassis number, and “ss” represents the number of the chassis slot containing the module. For more information about the LIST function, refer to Publication 1775–800, PLC–3 Installation and Operation Manual.

Module Options

Selecting option 1 MODULE OPTIONS from the above menu (section titled Programmable Configuration Parameters) causes LIST to present the following menu:

KA – nn MODULE OPTIONS 1 TIMEOUT 2 SEND UNPROTECTED

221

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3 ACCEPT UPLOAD/DOWNLOAD 4 ACCEPT WRITES 5 BACKUP OPERATION 6 PLC–2 MASK ENTER NEXT>

This menu allows you to select options that apply equally to both the modem port and the Data Highway port of the 1775–KA module. These options are described below.

Timeout

The timeout is the maximum amount of time that the 1775–KA module will wait for another station to reply to one of its messages. The allowed entries are 0 to 9999, expressed in increments of 1/10 second. LIST displays the timeout as “xxxx/10 SEC”. Thus, if you enter a timeout value of 100, the timeout period will be 10 seconds and will be displayed as 100/10 SEC.

The same timeout setting applies to both the Data Highway and the modem ports. The default timeout setting is 5 seconds, displayed as 50/10 SEC.

The timeout period applies to each individual transmission. Because of their size, some messages consist of several packets of data. Each message packet requires a separate transmission. Therefore, the timeout is restarted for each packet.

If the 1775–KA module waits longer than the timeout period for a reply to one of its messages, it generates an error code of 37 (Appendix B). The module then resumes executing the current message procedure at the line following the one in which the timeout occurred.

LIST keeps you at this timeout level and allows you to make repeated changes to the timeout value. To return to the preceding (next highest) level of LIST, press the ENTER key again without entering a new timeout value.

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Send Unprotected

This option determines whether or not the 1775–KA module will be able to send unprotected command messages to other stations. If you select option 2 SEND UNPROTECTED, the 1775–KA module will be able to send both protected and unprotected commands.

You can use an unprotected command to read or write to any area of a PC data table. You can use a protected command, however, to write only to those areas of a PC data table specified by the PC that receives the command. For more information on protected and unprotected commands, see section titled Access Privileges, chapter 3.

If you do not select (enable) this option, the module will be able to transmit only protected commands. At initial power–up, the module enables the SEND UNPROTECTED option by default.

Accept Upload/Download

This option determines whether or not the 1775–KA module will be able to execute upload and download commands sent to it by a computer. If option 3 ACCEPT UPLOAD/DOWNLOAD is selected, the module will be able to execute both upload and download commands. You send a sequence of upload and download commands when you want to transfer the memory of the PLC–3 to another station, or to transfer the memory of another station to a PLC–3.

If this option is not selected (enabled) the module will not be able to execute either of these two types of commands. For a description of upload and download commands, refer to Appendix A. At initial power–up, the module enables the ACCEPT UPLOAD/DOWNLOAD option by default.

Accept Writes

This option determines whether or not the 1775–KA module will accept write–type command messages from a remote Data Highway station when the local PLC–3 processor’s memory protect keyswitch is on. If option 4 ACCEPT WRITES is selected, the module will accept write commands regardless of the setting of the PLC–3’s memory protect keyswitch. If this option is not selected (enabled) the module will accept write commands when the memory protect keyswitch is off but will reject the write commands and return an error code of 86 if the memory protect

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keyswitch is on. At initial power–up, the module enables the ACCEPT WRITES option by default.

Backup Operation

This option determines whether or not a pair of 1775–KA modules will provide backup for each other. Enable option 5 (BACKUP OPERATION) for both the primary and backup 1775–KA modules to enable backup operation as described in section 2.3 (backup configurations). If you make no selection for option 5, backup operation is disabled by default. The revision C or earlier version of the module does not have the BACKUP OPERATION option.

PLC–2 Mask

This option determines whether or not the 1775–KA module will mask out the upper octal digit of the source address when receiving a PLC–2 type command from another station. If you enable option 6 (PLC–2–MASK) the module mask out the upper digit of the address for selecting the input file. This causes stations with common second and third digits of their address to access the same input file. For example, stations 023, 123, 223, and 323 would all access input file 023.

If you disable option 6, each station accesses a unique input file with the same number as the station number. For example, station 123 would access input file 123; station 223 would access input file 223. If you make no selection for option 6, the PLC–2 MASK option is disabled by default. The revision D or earlier version of the module does not have the PLC–2 MASK option.

Data Highway Port

Selecting option 2 DATA HIGHWAY PORT from the above menu (section titled Programmable Configuration Parameters) causes LIST to present the following menu:

224

KA – nn DATA HIGHWAY PORT 1 ENABLE/DISABLE PORT 2 STATION NUMBER 3 BAUD RATE ENTER NEXT>

Chapter 2

Installation

This menu allows you to select options that apply to only the Data Highway port of the 1775–KA module. These options are described below.

Enable/Disable Port

This option determines whether or not the 1775–KA module can communicate over the Data Highway. you must select the ENABLE option in order to allow communication to take place. If you make no selection, the PLC–3 disables this port by default.

Note, however, that you cannot use LIST to change any other parameters of the Data Highway port unless you first DISABLE the port. After you are done entering parameters through LIST, don’t forget to ENABLE the Data Highway port again.

Station Number

This option selects the number by which the PLC–3 station is identified on the Data Highway. Allowable station numbers are 1 to 376 octal. In particular, note that the number 377 is illegal. Entering 377 as the station number will automatically disable the 1775–KA module, and you will not be able to ENABLE it again through LIST until you select a different station number. If you make no selection, the PLC–3 assumes the illegal address 377 by default.

Baud Rate

This option specifies the communication rate over the Data Highway. A communication rate of 57,600 baud is recommended.

Modem Port

Selecting option 3 MODEM PORT from the above menu (section titled Programmable Configuration Parameters) causes LIST to present the following menu:

KA–NN modem port 1 ENABLE/DISABLE PORT 2 STATION NUMBER 3 BAUD RATE 4 COMMUNICATION MODE

225

Chapter 2

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5 EVEN PARITY 6 SEND EMBEDDED RESPONSES ENTER NEXT>

This menu allows you to select options that apply to only the modem port of the 1775–KA module. These options are described below.

Enable/Disable Port

This option determines whether or not the 1775–KA module can communicate through its RS–232–C port. You must select the ENABLE option in order to allow this communication to take place. If you make no selection, the PLC–3 disables the RS–232–C port by default.

Note, however, that you cannot use LIST to change any other parameters of the RS–232–C port unless you first disable the port. After you are done entering parameters through LIST, don’t forget to enable the RS–232–C port again

Station Number

This option selects the number by which the PLC–3 station is identified on an RS–232–C communication link. In particular, note that the number 377 is illegal. Entering 377 as the station number will automatically disable the RS– 232–C port of the 1775–KA module, and you will not be able to enable it again through LIST until you select a different station number. If you make no selection, the station number will be 377 by default.

Baud Rate

This option specifies the communication rate over the RS–232–C port. The choices are:

110 baud 2400 baud 300 baud 4800 baud 600 baud 9600 baud 1200 baud 19200 baud

226

For long–line communication, the maximum allowed rate is 4800 baud. The default baud rate is 1200 baud (see Table 2.D).

Chapter 2

Installation

Communication Mode

This option determines whether the RS–232–C port of the 1775–KA module can operate in a half–duplex (polled) or full–duplex (unpolled) mode. Select full– duplex for point–to–point communication through the RS–232–C port. Select half–duplex if the 1775–KA module is installed as a slave station on a multipoint modem link. If you make no selection, the 1775–KA selects the full– duplex (unpolled) mode by default.

Even Parity

This option determines what kind of parity check is used for all communications through the RS–232–C port. If option 5 EVEN PARITY is selected, the 1775–KA module will test for even parity in all communications through its RS–232–C port. If this option is not selected, the module will not perform any parity checking. At power–up, the PLC–3 disables the even parity option by default.

Backup Configurations

Send Embedded Responses

This option determines whether or not the 1775–KA module will be able to send embedded responses through its RS–232–C port. Responses are acknowledgments (ACKs or NAKs) to messages received from other stations. An embedded response is one whose characters are transmitted between the bytes of a regular message. In this way, the response to a previously received message is transmitted along with a new message. At power–up, the PLC–3 disables the embedded responses option by default.

The 1775–KA module can combine with the PLC–3 processor to form a backup system. System backup is described in greater detail in the PLC–3 Programmable Controller Backup Concepts Manual (pub. no. 1775–6.3.1). The following discussion is an overview of system backup and the role of the 1775–KA in various backup procedures.

There are two possible backup configurations for the 1775–KA module:

Two 1775–KA modules in the same PLC–3 controller One 1775–KA module in a primary PLC–3 controller and another

1775–KA in a backup PLC–3 controller

The first configuration provides backup for the 1775–KA module itself. Here, both 1775–KA modules are always active, and both are independent stations on their communication network. Therefore, each 1775–KA

227

Chapter 2

Installation

module must have its own unique station number. If you want to send the same message through both 1775– KA modules, you must program the two separate message instructions.

The second configuration provides system backup for the PLC–3 controller.

If the 1775–KA modules are Rev. C or earlier, you:

1. Assign different station addresses to each communication adapter

module.

2. If the programs in the primary and backup processors are identical:

you must be sure that all information sent to the primary processor is

also sent to the backup processor.

you must examine the run/backup bit (data table status section, file 0,

word 3, bit 17) on every rung used to transmit data. This bit is set in the primary processor and reset in the backup processor. Examining it helps to prevent sending duplicate messages over the Data Highway.

If the 1775–KA modules are Rev. D or later, you can:

follow the two steps described above

select BACKUP OPERATION with the PLC–3 LIST function.

To implement backup operation, follow these steps:

1. Using the option switches on both 1775–KA modules, set switch 2 to

the OPEN position. Recall (section titled Option Switches) that this causes the module to disable its Data Highway port if the PLC–3 becomes deactivated.

WARNING: If you do not set these switches OPEN on both 1775–KA modules, these modules will assume the same station address when the primary PLC–3 becomes deactive. This may shut down communication on the Data Highway, and unexpected machine motion may result.

228

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2. Use the LIST function to disable the modem and Data Highway

ports.

3. Use the LIST function to select BACKUP OPERATION for both the

primary and backup 1775–KA modules. For more information, see the PLC–3 Installation and Operation manual (publication 1775–6.7.1). Thus, when you select BACKUP OPERATION, the condition appears like this:

5*BACKUP OPERATION

4. Use the LIST function to assign the same station address to the

modules for the primary PLC–3 and the backup PLC–3 processor.

You can never give the 1775–KA module a station address of 3778, and when you select the BACKUP OPERATION, you can not give the module an address of 2778.

Because you have chosen BACKUP OPERATION, the module in the backup PLC–3 will assume an address other than the address you assign it with the LIST function (Figure 2.12).

You assign both modules an identical address.

the address

is between:

0018 and 276

3008 and 376

The backup module assumes

an address that is:

1008 higher than the primary module

2008 lower than the primary module

At switchover, the address for the backup module returns to the station address you assigned to it with the LIST function.

5. Use the LIST function to enable whichever (Data Highway or

Modem) port you are using to connect primary to backup.

229

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Figure 2.12

addresses of the primary and backup PLC-3 controllers change during switchover

How

Before switchover: Primary PCL–3 Backup PLC–3

You set these station addresses: 010

The module assume the station addresses:

010

010 110

After switchover:

You previously set these station addresses: 010

The module assume the station addresses:

Backup PLC–3

110

Primary PCL–3

010 010

10013–I

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Using Manual Switchover

After you select the BACKUP OPERATION for a rev. D. (or later) 1775–KA module, you may choose to use your PLC–3 backup system for manual switchover. In manual switchover, you must initiate the switchover by changing the position of a switch in a backup cable. (Refer to the PLC–3 Programmable Controller Backup Concepts Manual, pub. 1775–803, for more details.) You must be sure to turn off the faulted PLC–3 processor before you begin the switchover, however.

a manual switchover occurs:

And: Then:

the PLC-3 processor is waiting for a response

another station on the Data Highway is initiating a message

you are only communicating with the primary PLC-3

the response is ignored

you may not receive a response from either PLC-3 processor program other stations on the Data Highway to recover from this condition

the other stations on the Data Highway will receive time-out errors for messages they send after the primary goes deactive and before switchover occurs.

. Y

ou must

You can program the MSG instruction to execute a message upon switchover or you can send commands to the backup PLC–3 processor (Figure 2.13). As long as you get responses from the backup processor, switchover has not yet occurred.

231

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E0000

S0003

NOTE:

Figure 2.13 Example PLC-3.

Bits E0000/00 and E0000/01 are internal storage bits. You can use any unused data table section to reference these bits. Bit S0003/17 is the run/backup bit.

of a Rung that Sends a Message during switchover from primary PLC-3 to backup

MSG MESSAGE TYPE CTL = FB200:00001 = 0 CHANNEL: E2.5. #H045$N4:17= $B3:5

STAT

EN 12

STAT

DN 15

STAT ER

E0000

Using Automatic Switchover

After you select the BACKUP OPERATION for a rev. D. (or later) 1775–KA module, you may want to use automatic switchover for your PLC–3 backup system. During automatic switchover:

the 1775–KA module for the primary PLC–3 processor disables its

Data Highway port.

the 1775–KA module for the backup PLC–3 processor becomes the

address that you selected with the LIST function (rather than the corresponding address it received during the BACKUP OPERATION).

NOTE: You cannot select the BACKUP OPERATION for a multidrop modem applications because the modem port will not become disabled after a PLC–3 processor fault regardless of the switch settings on the module.

232

an automatic switchover occurs:

And: Then:

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Installation

the PLC-3 processor is waiting for a response

another station on the Data Highway is initiating a message

another station is communicating with the primary PCL-3 processor

the response is ignored

possibly neither of the PLC-3 processors will respond to the message. Y other stations on the Data Highway to recover from this condition

the other station will receive no indication that a switchover has occurred. Y however execute a message upon switchover (fig.

2.13) or send commands to the backup PLC-3 processor communicate with the backup, you know that no switchover has occurred

, program a MSG instruction to

. If you are able to

ou must program

ou can,

Run/Backup Bit

It is important to alert the proper personnel when a switchover occurs. One way you can provide such indication is by having your program monitor the run/backup bit (data table status section, file 0, word 3, bit 17) and turn on alarms or lights when the status changes from backup to run. This bit is set in the primary processor and reset in the backup processor.

Multiple 1775-KA Modules in One PLC-3

It is also possible to link a single PLC–3 controller to more than one Data Highway by installing multiple 1775–KA modules in the same PLC–3. In this configuration, each 1775–KA module connects to a different Data Highway, and each has a unique station number on its associated highway. However, all the 1775–KA modules in the same PLC–3 controller can have either the same or different station numbers.

CAUTION: If such a PLC–3 station is communicating through a PLC/PLC–2 buffer file and all of the stations’ 1775–KA modules have the same station number, then all of these modules will transfer data through the same buffer file. This can cause unpredictable results if several 1775–KA modules try to read or write to the buffer file at the same time.

When such a PLC–3 station transmits a command message to a remote Data Highway station, the thumbwheel number specified in the PLC–3 message instruction (section titled PLC–3 Stations) determines which 1775–KA module actually transmits the command.

233

Chapter

Data Highway Communication

General

Some Terminology

This chapter introduces some of the concepts and terminology involved with operating the 1775–KA module of the Data Highway.

The Allen Bradley Data Highway is a communication network for industrial control applications. The Data Highway consists of a central trunkline cable that may be up to 10,000 feet long. This cable can link together as many as 64 distinct communication points (or nodes) called stations.

Each station consists of some type of processor and a station interface module. The station interface module enables the processor to communicate with other stations on the Data Highway. The 1775–KA module is the station interface module for the PLC–3 processor. Table 3.A lists all possible combinations of station interface modules and processors.

Table 3.A

Components

Station

Processor

Station Interface Module

PLC-4 Microtrol

PLC-3

PLC-2 Family

PLC

Computer or other

programmable

RS-232-C compatible

device

Communication Terminology

Stations communicate with each other by sending messages over the Data Highway. There are two types of messages:

Command messages Reply messages

1773-KA Communication Interface Module

1775-KA Communication Adapter Module

1771-KA Communication Adapter Module

1774-KA Communication Adapter Module

1771-KC/KD/KE/KF Communication Controller Module

31

Chapter 3

Data Highway Communication

A command message either gives (writes) data to, or requests (reads) data from, one station to another. A reply message is a station’s response to a command message.

Command messages are generated by message procedures that you program into the 1775–KA module. Execution of a message procedure is controlled by the message (MSG) instruction in the PLC–3 ladder diagram program. When a 1775–KA module receives a command message from another station, the module automatically generates the appropriate reply message.

As points of reference, we can talk about local and remote stations. The local station is the one currently initiating some action, or the one we are currently doing something with. All other stations are then remote.

We can also describe stations in terms of their relationship to a message. The transmitting station is the one sending the message, and the receiving station is the one that gets the message. A station that transmits a command message is called a command station, and a station that transmits a reply message is called a reply station.

You can send either:

a single message procedure command (Chapter 6) that may be up to 76

characters long.

the name of a Data Highway message procedure which contains a

group of commands and is stored in the 1775–KA module

You specify the station that will receive the command with a PLC–3 extended address. This address always takes the form:

E2.5.nn

where

E2 specifies that this command addresses the module status area of PLC–3 memory

32

5 specifies that you are sending the message instruction through the 1775–KA module

nn is replaced with the thumbwheel setting on your particular 1775–Ka module

Chapter 3

Data Highway Communication

To enter a message instruction, complete the steps below:

1. Enter a condition that, when true, will activate the message

instruction. In Figure 3.1, we used an examine–on for input word 0012

, bit 01.

Figure 3.1

of Programming in Data Highway Communication

Levels

1) PLC–3 Processor

Ladder Diagram Program

MSG

10012

Message instruction to execute message procedure PROC_A

3) Data Highway

DLE STX DST SRC CMD STS TNSW ADDR SIZE

MESSAGE TYPE 1 CTL = FB200:0000=200 CHANNEL: E2.5.1

@PROC_A

STAT

EN 12

STAT

DN 15

STAT

ER 13

2) 1775–KA Module

Data Highway Message Procedure PROC_A

#H024$B12:37 = 15

Message procedure command to transmit a message to data highway station number 24

DATA

(OPTIONAL)

DLE EXT BCC

Command message transmitted to station 24

10014–I

33

Chapter 3

Data Highway Communication

2. Press the message instruction key.

3. Specify message type 1.

4. Choose a control file word where status information about the

message command can be stored. In our Figure 3.1, we used binary file 200, word 200.

Data transfers can be either solicited or unsolicited, depending on whether they are initiated by the local or a remote station, respectively. Either type of station initiates the data transfer by issuing a command message. If the local station issues the command message, the corresponding reply message is said to be solicited because the local station has solicited, or requested, the data contained in the reply message. If a remote station issues the command message, that message is said to be unsolicited.

Levels of Programming

For solicited messages, a local station receives data from a remote station during a read operation. The local station sends data to a remote station during a write operation.

For unsolicited messages, a local station receives data from a remote station during a write operation. A local station sends data to a remote station during a read operation.

In read operations, the command message requests the data transfer, but the corresponding reply message actually contains the data being transferred. In write operations, the command message contains the data being transferred, and the reply message merely reports the status (receipt or non–receipt) of the transfer.

The PLC–3 processor must be free to control its own processes at the same time that the 1775–KA module is communicating over the Data Highway. For this reason, both the processor and the module have their own programs and programming languages. Figure 3.1 illustrates how these two programming levels (processor and module) interrelate.

34

PLC-3 Program

The first link in the communication process is your PLC–3 ladder diagram program. You send a Data Highway command message by means of the message (MSG) instruction. Figure 3.1 shows a typical MSG instruction.

Chapter 3

Data Highway Communication

When the rung becomes true, the message instruction begins sending command(s) across the Data Highway. At the same time, bits in a control file word change their state (Table 3.B) to reflect the status of the command. Even if the rung becomes false, the message command will continue to send commands across the highway.

Table 3.B

Status of Bits in a Control File W

The

WHEN:

the message instruction is true

the enable bit (16) is set the latched enable bit (12) is set

the remote Data Highway module has received the message instruction

the request bit (17) is set

the 1775-KA module begins operation

the busy bit (14) is set

the operation is complete

the busy bit (14) is set either the done bit (15) or the error bit (13) is set

the rung becomes false

the request bit (17) is reset the busy bit (14) is reset the enable bit (16) is reset the latched enable bit (12) is reset

the rung becomes true a second time

either the done bit (15) or the error bit (13) is reset

ord

5. Enter an extended address for the channel. In our Figure 3.1, we

address the module status area of memory, specify the 1775–KA module, and a thumbwheel setting of 1.

6. Enter either a command or a command procedure. In Figure 3.1, we

entered the command procedure, PROC_A.

Data Highway Message Procedure

As already stated, the 1775–KA module has its own programming language that consists of commands (Chapter 8). A group of related commands make up a Data Highway message procedure. These commands and message procedures determine what messages are transmitted over the Data Highway.

35

Chapter 3

Data Highway Communication

Data Transfers

The whole purpose of Data Highway communication is to transfer data from one station processor memory location to another. To accomplish these data transfers, you can program the assignment command into the 1775–KA module.

Chapter 6 gives the details of the assignment command. For now, let’s just look at the simple example in Figure 3.2. In this example, the assignment command copies a word (16 bits) of data from the source to the destination location. The source of the data is always specified on the right of the equals sign (=), and the destination is always on the left.

Figure 3.2 Example

Assignment Command

$B45:21 = $I12:33

Source Address

Address Delimiter Asignment Command

Destination Address

Address Delimiter

36

10015-I

Note that an assignment command does not destroy the data at the source location; rather, it just makes a copy of the source data at the destination location. When the assignment is executed, both source and destination will contain the same data.

There are two ways to use a data transfer command with the 1775–KA module:

as a single command within a PLC–3 message instruction as one of multiple commands within a message procedure

Figure 3.3 illustrates both of these methods for the same assignment command. Note that a message instruction in the PLC–3 ladder diagram program controls execution of the command in either case.

Figure 3.3

ays to Use 1775-KA Commands

Two

Chapter 3

Data Highway Communication

1) as a single command in a PLC–3 message instruction

MSG

10012

MESSAGE TYPE 1 CTL = FB200:0000=200 CHANNEL: E2.5.1 $B45:21=$112:33

STAT

EN 12

STAT

DN 15

STAT

ER 13

2) as part of a message procedure

Message Procedure PROC_A

(other commands)

$B45:21 = $112:33

(other commands)

PLC–3 Message Instruction to Control Execution of Procedure PROC_A

MSG

10012

MESSAGE TYPE 1 CTL = BW200:0000=200 CHANNEL: E2.5.01 @ PROC_A

STAT

EN 12

STAT

DN 15

STAT

ER 13

10016–I

37

Chapter 3

Data Highway Communication

Access privileges

Not every Data Highway station can read or write to every other station. In general, read and write access privileges depend on two factors:

type of processor at the transmitting and receiving stations protections set at the receiving station

The rest of this section explains how these access privileges vary according to the above factors.

PLC–3 Stations

A PLC–3 station can always read data from any major area of another PLC–3’s memory. However, one PLC–3 station can write only to the data table area of another PLC–3 station.

In addition, a local PLC–3 station can prevent remote PLC–3 stations from writing to the local station’s data table by setting a memory protection switch. At the local station, the memory protect switch can be overridden by selecting option 4 in the Module Options Menu (section titled Accept Writes, chapter 2) at the local station.

PLC/PLC–2 Stations

For communication with a PLC or a PLC–2 station, read, and write access privileges depend on switch settings at that station. For an explanation of how to set the switches for read and write access, refer to the Communication Adapter Module User’s Manual (publications 1771–6.5.1 and 1774–6.5.8).

Accessing a PLC/PLC–2 Station

Access to a PLC/PLC–2 station also depends on the type of command transmitted to that station. There are two types of commands:

protected write commands unprotected read and write commands

Protected write commands can only write to specified sections of the data table in a PLC/PLC–2 processor. Memory access rungs in the PLC/PLC–2 ladder diagram program specify where in the data table the PLC–3 can write data.

38

Unprotected commands, on the other hand, can read or write to any section of the data table at a PLC/PLC–2 station. (Again, refer to publication 1771–801 or 1774–819 for an explanation of protected and unprotected commands and memory access rungs.)

Chapter 3

Data Highway Communication

A PLC–3 station can read from any part of a PLC/PLC–2 data table. However, A PLC– 3 station cannot write to a PLC/PLC–2 if the switch settings at the PLC/PLC–2 station forbid access. If the switches at the PLC/PLC–2 station are set to accept only protected write commands, then the ladder diagram program at the PLC/PLC–2 station must contain memory access rungs to define which areas of the PLC/PLC–2 station’s data table are accessible. In such a case, a transmitting PLC–3 station can write to only those data table areas defined by the memory access rungs, and only by means of protected write commands. If the switches at the PLC/PLC–2 station are set to accept unprotected write commands, a PLC–3 station can then write to any area of the PLC/PLC–2’s data table by transmitting an unprotected write command (section titled Command Message Type chapter 6).

Accessing a PLC–3 from a PLC/PLC–2 Processor

While a PLC–3 processor can address any area of a PLC/PLC–2 data table, a PLC/PLC–2 reads an input file that is a part of the PLC–3 data table. That file 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)

[1]

Station address 000 is assigned to input file I008. Otherwise PLC-3 input files with an 8 or 9 in their address are not used for read/write access by a PLC-PLC-2 station (except I008 for station 0).

Station

000 I008

001 I001

002 I002

003 I003

004 I004

005 I005

006 I006

007 I007

010 I010

011 I011

012 I012

. .

077 I077

100 I100

Assigned PLC-3 Input File

for Read/W

rite Access

[1]

39

Chapter 3

Data Highway Communication

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 address are not used for read/write access by a PLC/PLC–2 station.

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 that file is created and allocated at the PLC–3. To create a PLC–3 file, use the CREATE command described in the PLC–3 Programming Manual (publication 1775–801).

Note that it is possible to have two PLC–3 stations communicate with each other as if they were PLC/PLC–2 stations. To do this, simply allocate the appropriate PLC/PLC–2 buffer files in the PLC–3 stations and uses the PLC/PLC–2 addressing format (section titled PLC/PLC–2 Address Specifications, chapter 4) in the assignment commands. Similarly, a computer can sent PLC/PLC–2 commands to a PLC–3 station by using the appropriate message packet formats (Appendix A).

To allow as many as 4 remote stations to access the same PLC–3 input file:

1. Enable the PLC–2 MASK option in the LIST function. PLC–2

MASK is option 6 on the Module Options menu.

2. Select station numbers 100

apart. For example, you could use

stations 010, 110, 210 and 310.

The stations will have access to the input file which matches the lower two digits of these station numbers (input file 10 in this example). When the 1775– KA module receives a PLC–2 type command, it masks the upper octal digit in order to determine which input file to access. So commands sent from stations 010, 110, 210, and 310 would all access input file 10.

310

Chapter 3

Data Highway Communication

PLC–4 Stations

To read or write to a PLC–4 station, you can send either protected or unprotected commands.

Switches 2 and 3 (on the second row of switches) at the 1773–KA module specify whether the PLC–4 station will accept unprotected and protected commands (respectively) through the Data Highway port of the 1773–KA module.

Switches 1 and 3 (on the third row of switches) at the 1773–Ka module specify whether the PLC–4 station will accept protected and unprotected commands (respectively) through the RS–232–C port of the 1773–KA module. In all cases, if the switch is set to the closed position, the module will accept that type of command.

311

Chapter

Addressing Rules and Examples

General

This chapter presents some general rules for specifying data addresses in message procedures. This chapter assumes that you are already familiar with the forms and meanings of addresses in the PLC–3 and other Allen–Bradley programmable controllers. For details on these subjects, refer to the appropriate documentation listed in Table 4.A.

Table 4.A Memory

Organization Documentation

Controller Document Publication

Number

(Old/New No.)

PLC-3

PLC

PLC-2

PLC-2/30

PLC-2/20

PLC-2/15

PLC-4

PLC-3 Programming Manual

PLC Programming & Operations Manuals

PLC-2 Memory Organization and Structure

PLC-2/30 Memory Organization

Memory Organization of PLC-2.20 Controller

PLC-2/15 Memory Organization

PLC-4 Microtrol Product Guide

1775-801/1775-6.4.1

1774-800/1774-6.8.1

1772-907/---------

1772-914/1772-4.4

1772-909/1772-4.3

1772-912/---------

1773-800/1773-6.5.1

In this chapter,the addressing formats are presented in shorthand notation. The notation used is as follows:

<bit>

the number of a particular bit within the

addressed word <fileaddr> <filesym> <offset>

the logical address of a PLC–3 file

a symbolic address of a PLC–3 file

the number of words between the

beginning of the file and the desired word

(offset is zero for the first word of a file) <size> <wordaddr> <wordsym>

number of words of data to be transferred

the logical address of a PLC–3 word

a symbolic address of a PLC–3 word

41

Chapter 4

Addressing Rules and Examples

An expression can be used in place of any of the above fields in an address.

Number Systems

Within the above listed fields of an address specification, numbers are interpreted as decimal (base 10) unless you indicate that they are octal (base 8). You can specify an octal number by enclosing the number in parentheses and starting it with a leading zero. For example, 17 is interpreted as decimal 17, but (017) is interpreted as octal 17, or decimal

15.

An exception to the above rule occurs when addressing a word in the input or output sections of PLC–3 memory. In these cases, the word address <wordaddr> is normally interpreted as an octal number, regardless of leading zeros. To express an input or output word address as a decimal value, enclose the word address within parentheses and eliminate leading zeros.

In addressing individual bits, parentheses have no affect on the address interpretation The bit address <bit> is interpreted as an octal number if it starts with a leading zero and as a decimal number if it does not start with a zero.

Figure 4.1 illustrates these addressing conventions.

42

Figure 4.1 Examples

Address Specification

I12:15

I12:15/15

I12:015/015

I12:(15)

I12:(015)

N43:15

N043:15

N(043):15

N(43):15 Integer file 43, word 13

of Addressing Conventions

Interpretation (expressed in decimal)

Input file 12, word 13

Input file 12, word 13, bit 15

Input file 12, word 13, bit 13

Input file 12, word 15

Input file 12, word 13

Integer file 43, word 13

Integer file 35, word 13

10017-I

Chapter 4

Addressing Rules and Examples

Addresses

Data is referenced by its address in memory. In a message procedure, you must precede an address with a dollar sign. The dollar sign acts as a delimiter to tell the 1775–KA module that it has encountered a data address. Figure 4.2 illustrates this addressing format in a simple assignment command.

Figure 4.2 Example

Assignment Command Showing Addressing Format

$B45:21 = $I12:33

Destination Source Address Address

Assignment Command

For data locations at remote stations, the remote station number must precede the data address. Figure 4.3 illustrates this addressing format. For communication on the Data Highway, the characters #H are required to delimit the remote station number. For RS–232–C communication through the 1775–KA module’s modem port, the characters #M delimit the remote station number.

10018-I

Figure 4.3 Example

#H024

of Remote Station Addressing in an Assignment Command

$B45:21 = $I12:33

Source Address Address Delimiter

Assignment Command Destination Address Address Delimiter Remote Station Number (octal)

Data Highway Port Identifier Remote Station Delimiter

10019-I

43

Chapter 4

Addressing Rules and Examples

Symbols

You can also use symbols to represent data and data addresses in message procedures. A symbol can consist of numeric digits, alphabetic characters, and the underline character (_). No other special characters are allowed. The first character in a symbol must be a letter of the alphabet.

Both upper–case and lower–case letters are acceptable in a symbol, but they are distinguished. For example, ASYMBOL and Asymbol are two different symbols.

A symbol can be any length, but it must be unique in its first 8 characters. For example, SYMBOL_A and SYMBOL_B are distinguishable in a message procedure, but NEW_SYMBOL_A AND NEW_SYMBOL_B are not. Note that indistinguishable symbols are not flagged as programming errors. Rather, indistinguishable symbols are treated as equivalents.

Certain words and character combinations cannot be used as symbols because they are reserved for special uses in message procedures. The reserved words are:

CREATE IF DELETE ON_ERROR ERROR PROT EXIT STOP GOTO UNPRO

Any abbreviated form of one of the above words is also invalid as a symbol. For example, the single letter C should not be used as a symbol because it is an abbreviation of the word CREATE. Similarly, PRO is an invalid symbol.

Figure 4.4 illustrates the classification of different types of symbols. The two major classifications are:

system symbols user symbols

44

Figure 4.4

Symbol

Chapter 4

Addressing Rules and Examples

ypes

User Symbol Generate value assignment command

Interprocedural Applies to the procedure in which it is generated plus any other procedure nested together with that procedure

this symbolic

through the

Symbol

Procedural Applies only to the procedure in which it is generated.

Procedure Name Applies to a single procedure or other procedures nested together procedure.

Global Applies to any context.

within that

System Symbol Generate this symbol with the Edit command (for a procedure name) or a Create command (for a symbolic address).

Symbolic Address Can

be used in place of a logical address.

Local Applies only to the context in which the symbol

is generated.

anywhere

10021–I

System Symbols

A system symbol is used as either a procedure name or a symbolic address. The characters in a system symbol must conform to the general rules given above for all symbols. System symbols are delimited by the character @, which distinguishes them from user symbols.

Procedure Names

A procedure name is a way of referring to a message procedure. You assign a procedure name at the time you generate, or edit, the message procedure (Chapter 6).

One procedure can execute a second procedure simply by stating the name of that second procedure. This allows for nesting of procedures up to three levels deep.

Symbolic Addresses

45

Chapter 4

Addressing Rules and Examples

A symbolic address is another way of representing the logical address of data (section titled Addresses). You can generate a symbolic address by using the CREATE command (Chapter 8). A symbolic address can be used anywhere that a logical address can be used in a message procedure. The symbolic address is stored in the system symbols area of the PLC–3 memory.

Scope of System Symbols

System symbols can be either local or global in scope. A global system symbol is known in any context. A local system symbol is known only in the context in operation at the time the symbol was generated. Context is explained in the PLC–3 Programming Manual (publication 1775–801).

At the time you generate the system symbol, you can specify whether it is to be local or global. If you do not specify the scope of the system symbol, it is assumed to be local.

Note that the terms local and global symbols should not be confused with local and remote stations. Both local and global symbols having meaning only at the station in which they were generated.

User Symbols

A user symbol represents a numeric value. You can generate a user symbol and assign a value to it by means of the assignment command (Chapter 7).

User symbols are either procedural or interprocedural. Procedural user symbols are known only to the procedure in which they are generated. Interprocedural user symbols are known to the procedure in which they are generated and to any other procedure nested within that procedure.

User symbols can contain data that is up to 32 bits long. If the high–order bits are insignificant (that is, if they can be truncated without changing the value of the data), then the contents of the user symbol can be stored in a data field that is less than 32 bits long. Attempting to put a data value into a field that is too small for it will generate an error code of 189 (Appendix B).

46

Chapter 4

Addressing Rules and Examples

PLC-3 Address Specifications

The PLC–3 processor uses logical addresses to reference data in memory. No PLC–3 address is valid unless it memory location has been allocated. You can allocate memory by using the CREATE command in PLC–3 programming. The PLC–3 Programming Manual (publication 1775–6.4.1) explains how to do this. Note that the CREATE command for memory allocation is different than the CREATE command for creating symbolic addresses (Chapter 6).

The following rules apply when specifying a PLC–3 logical address in a message procedure:

1. Symbolic addresses must be defined to either the word level or the

file level of specification.

2. A word address may be either: (a) a block address specified to the

word level, (b) a symbolic address of a word, or (c) a symbolic file address followed by a colon (:) and an offset.

3. A size specification must be preceded by a word address and a

comma (,).

4. An offset specification must be preceded by a file address and a

colon (:).

5. A bit number must be preceded by a word address and a slash (/).

6. To access the pointer or floating point sections of memory, extended

addressing must be used.

These rules are applied in the formats given below for addressing PLC–3 data locations.

Addressing a File

The format for addressing a PLC–3 file is one of the following:

For assignment commands that copy data from one file to another, both the source and the destination file must be exactly the same size.

47

Chapter 4

Addressing Rules and Examples

For PLC–3 timer and counter files, it is important to note that the data words are stored in the following order:

CTL PRE ACC

That is, the control, preset, and accumulated values for a given timer or counter are stored as consecutive words in the same file.

Addressing a Word Range

To address a range of words in PLC–3 memory, use one of the following formats:

Figure 4.5 is an example of addressing a range of PLC–3 words.

Figure 4.5 Example

of Addressing a Range of PLC-3 W

ords

$N 15 : 0, 20

Address of first word to be transferred.

Delimiter

You may use a word range only as the source field in an assignment command. The destination must be a file that is as large as, or larger than, the source range.

Number of words to be transferred

10022-I

48

Addressing a Word

To address a single word in PLC–3 memory, use one of the following formats:

Chapter 4

Addressing Rules and Examples

Note that <wordaddr>is interpreted as an octal value if the addressed word is in an input or output file. Otherwise, <wordaddr>is interpreted as a decimal value (section titled Number Systems).

To access words in the pointer of floating point sections of PLC–3 memory, use the PLC–3 extended addressing format. You can read about extended addressing in:

PLC–3 Programmable Controller Programming Manual (pub. no.

1775–6.4.1)

Addressing a Bit

To address a specific bit within a PLC–3 word, use one of the following formats:

Figure 4.6 gives some examples of addressing individual bits in PLC–3 memory.

49

Chapter 4

Addressing Rules and Examples

Figure 4.6 Example

of Addressing Specific Bits in PLC-3 Memory

@FILE_A:16/8

$B1:5/012

Bit number 8 (decimal) Delimiter

Word offset from bewginning of file Delimiter Symbolic address of file

Bit number 8 (decimal) Delimiter

PLC/PLC-2 Address Specifications

Logical word address

10023-I

The PLC and PLC–2 processors use logical data addresses. These addresses are usually specified as octal numbers. However, the 1775–KA module interprets these addresses as decimal numbers unless they contain leading zeros (section titled Number Systems). Therefore, if you want to specify a PLC or PLC–2 word address as an octal number, begin the number with a 0(zero).

Addressing a Word Range

To address a range of words in PLC or PLC–2 memory, use this format:

Figure 4.7 illustrates this addressing format

You may use a word range only as the source field in an assignment command.

410

Chapter 4

Addressing Rules and Examples

Figure 4.7 Example

of Addressing a Range of PLC/PLC-2 W

ords

#H024$015,4

Addressing a Word

To address a single word in PLC or PLC–2 memory, use this format:

Number of words to be transferred (decimal) Delimiter

Word offset from beginning of memory (octal)

Address delimiter

Remote station number

Remote data highway station delimiter

10024–I

Addressing a Bit

To address an individual bit in PLC or PLC–2 memory, use this format:

Figure 4.8 illustrates this addressing format.

411

Chapter 4

Addressing Rules and Examples

Remote Station Address Specifications

Figure 4.8 Example

of Addressing Specific Bits in PLC/PLC-2 Memory

#H015$0121/010

To specify the address of data at a remote station, use the format shown in Figure 4.9. This format applies to both PLC–3 and non–PLC–3 remote stations. The characters #H delimit a remote Date Highway station, and the characters #M delimit a remote modem station.

Bit number 10 (octal)

Delimiter Word offset from beginning of memory (octal)

Address delimiter

Remote station number

Remote data highway station delimiter

10025–I

Figure 4.9 Example

of Addressing a W

ord in a Remote PLC-3 Station

#H 020 $ B 15:9

Word address at remote station

Address delimiter

Remote station number 20 (octal) Port identification for data highway port Remote station delimiter

#H 020 @ WORD_9

Remote station addresses are subject to the following restrictions:

Symbolic word address defined at remote station Remote station number 20 (octal)

Port identifier for data highway port Remote station delimiter

10026-I

412

Chapter 4

Addressing Rules and Examples

1. A remote address can be used only with the single equals sign (=)

type of assignment command.

2. In the assignment command, either the source or the destination, but

not both, may be a remote address.

3. A remote address may contain an embedded expression, but a remote

address may not be embedded in an expression.

Expression

Expressions use operators to combine two or more numeric values into a single value. Table 4.B lists the operators that can be used in an expression. These operators are listed from highest priority (1) to lowest priority (10). Expressions may be nested within other expressions by enclosing the inner expression within parentheses.

Table 4.B Expression

Operators

Operator Operation

.NOT.

or .BNOT

Bit operator

Logical complement

Bitwise 32-bit complement

Multiplication of 32 bits

Division of 32 bits

Addition of 32 bits

Subtraction of 32 bits

Order of

Execution

& or .BAND.

or .BXOR. Bitwise 32-bit EXCLUSIVE OR

or .BOR.

.EQ.

.GT.

.GE.

Left arithmetic shift

Right arithmetic shift

Bitwise 32-bit AND

Bitwise 32-bit OR

Compare equals

Compare greater than

Compare greater or equal

413

Chapter 4

Addressing Rules and Examples

Operator

Order of

ExecutionOperation

.LT.

.LE.

.NE.

.AND.

.OR.

Compare less than

Compare less or equal

Compare not equal

Logical AND

Logical OR

The result of an expression depends on the order in which the operators are executed. The order of execution depends on the type of operator and on left– to–right placement within the expression. Table 4.B gives the order of execution for the different operators. For example, the command

$B67:45 = 6+3*2

would store the value 12 in word 45 of binary file 67. This is because multiplication is performed before addition.

If an expression contains several operators with the same order of execution, those operators will be executed in the left–to–right order in which they appear within the expression. Extra set of parentheses can be nested within each other to change the order of execution. In such cases, the expression within the inner–most set of parentheses is evaluated first. For example, the command

414

$B67:45=36%((6+3)*2)

would store the value 2 in word 45 of binary file 67 (% is the operator for division).

Expressions can be used anywhere that direct numeric values can be used within a message procedure, including within an address field. For example, in the statement

$B67:(WORD+3)=5

the expression (WORD+3) specifies the address of a word within binary file 67. Note that the parentheses are necessary to indicate that +3 is part of the word address in this case.

Chapter 4

Addressing Rules and Examples

Number Systems

Within an expression, direct values are always interpreted as decimal (base 10) numbers unless you indicate that they are octal (base 8). You can specify an octal value by starting the number with a leading zero. For example, 17 in an expression is interpreted as decimal 17, but 017 is interpreted as octal 17 (or decimal 15).

Operators

This section describes the operators listed in Table 4.B.

Bit Operator

The bit operator allows you to address a specific bit of a value stored under a user symbol. For example, the statement

$I12:24/7=US_3/4

puts the value (0 or 1) of bit number 4 of user symbol US_3 into input file 12, word 24, bit 7.

The bit address itself can also be a user symbol or an expression. For example, in the statement

$I12:24/7=US_3/(4+US_1)

the expression (4+US_1) specifies a particular bit within user symbol US_3.

Note that the value appearing after the bit operator must be within the range of values allowed for bit addresses. Since user symbols are 32–bit values, a bit address for a user symbol must be in the range of 0 to 31 (decimal). Bit addresses for data table words must fall in the range of 0 to 15 (decimal).

Logical Operators

The logical operations are complement, AND, and OR. These operations are used to construct logically true or false conditions. They are generally used in decision statements such as the IF command (see section titled IF Command, chapter 6).

415

Chapter 4

Addressing Rules and Examples

The result of a logical complement is 1 (true) if the expression following the .NOT. is a value of 0 (zero). Otherwise, the result is 0 (false). For example, consider the command

$I12:24=.NOT.SYMBOL_A

If the value of SYMBOL_A is 0 (zero), then a 1 is stored in word 24 of input file 12. If the value of SYMBOL_A IS anything other than 0, then a 0 (zero) is stored in word 24 of input file 12.

The result of a logical AND is 1 (true) if the expression preceding the .AND. and the expression following the .AND. are both non–zero. Otherwise, the result is 0 (false).

The result of a logical OR is 1 (true) if either the expression preceding the .OR., the expression following the .OR., or both expressions are non–zero. Otherwise, the result is 0 (false).

Bitwise 32–Bit Operators

Bitwise 32–bit operators manipulate the individual bits in a 32–bit operand.

The bitwise 32–bit complement (.BNOT.) inverts the state of each bit in the 32– bit expression. That is, bits set to 1 are inverted to 0, and bits set to 0 are inverted to 1.

The bitwise 32–bit AND (.BAND.) forms a bit–by–bit logical AND of two 32–bit operands. There is no carry from one bit position to the next within the operand. For example, if

A contains the bit pattern 10101010010011110010101010101011

416

B contains the bit pattern 01110101011100100010101110001010

then the assignment C=A.BAND.B yields

C contains the bit pattern 00100000010000100010101010001010

Chapter 4

Addressing Rules and Examples

The bitwise 32–bit EXCLUSIVE OR (.BXOR.) forms a bit–by–bit logical EXCLUSIVE OR of two 32–bit operands. There is not carry from one bit position to the next within the operand.

The bitwise 32–bit OR (.BOR.) forms the bit–by–bit logical OR of two 32–bit operands. There is not carry from one bit position to the next within the operand.

Arithmetic Operators

The arithmetic operations are addition, subtracting, multiplication, and division. These are binary (not BCD) operations that produce 32–bit signed integer results.

A result from these arithmetic operations should normally be assigned to a 32– bit destination. The result can be assigned to a 16–bit destination only if the result is small enough in absolute value (less than 65,535) to fit into 16 bits. If the result is assigned to a 16–bit destination but is too large to fit into 16 bits, then an error code of 215 results.

There is no indication of overflow or underflow conditions with arithmetic operations.

Shift Operators

When a left arithmetic shift (<<) is executed, zeros are shifted into the rightmost bits of the expression. The leftmost bit are shifted out of the expression and are lost.

When a right arithmetic shift (>>) is executed, the leftmost bit of the expression does not change. If the leftmost bits is a 1, then 1’s are shifted in from the left. If the leftmost bit is a 0 (zero), then 0’s are shifted in from the left. Since the leftmost bit of an expression is the sign bit, this means that the right arithmetic shift does not change the sign of a numeric value. The rightmost bits are shifted out of the expression and are lost.

Comparison Operators

Comparison operators result in a value of 1 if the comparison is true and 0 (zero) if the comparison is false. For example, consider the command

$I12:23 = ($CACC:1.GE.$CACC:2)

417

Chapter 4

Addressing Rules and Examples

If the accumulated value of counter 1 is greater than or equal to the accumulated value of counter 2, then the number 1 is stored in word 23 of input file 12. If the accumulated value of counter is less than the accumulated value of counter 2, a value of 0 (zero) is stored in word 23 of input file 12.

Resulting Values

The result of an expression is a 32–bit value. If the high–order bits are not significant (that is, if they can be truncated without changing the value of the expression), then the result can be stored in a data field that is less than 32 bits long. Attempting to put a value into a field that is too small for it results in an error code of 215 (Appendix B).

418

Editing

Chapter

General

This chapter explains how to create and edit message procedures and commands for the 1775–KA module. The message procedure commands themselves are described in Chapter 6.

The general steps for editing a 1775–KA message procedure are:

1. Create and edit the PLC–3 ladder diagram program containing

message instructions to control execution of the 1775–KA message procedure.

2. Allocate memory to the necessary PLC–3 data files.

3. Create and edit the 1775–KA message procedure.

You can perform the first two steps through an Industrial Terminal (cat. no. 1770–T4) connected to the I/O Scanner–Programmer Interface Module (cat. no. 1775–S4A). The third step can be performed either through an Industrial Terminal or through a data terminal connected to the I/O Scanner–Message Handling Module (cat. no. 1775–S4B). These steps are described below.

Editing the Message Instruction

Table 5.A gives an example of how to edit the message instruction in the PLC–3 ladder diagram program. For more details on this type of editing, refer to the PLC–3 Programming Manual (publication 1775–801).

51

Chapter 5

Editing

System Prompt

ENTER FILE ADDRESS

ENTER SYSTEM ADDRESS OR SYMBOL

ENTER MESSAGE TYPE

Table 5.A Example

of Message instruction Editing

Action

Start edits.

Insert rung.

Enter the energize bit for the message rung. In this case, binary file 0, word 0, bit

Enter the message instruction.

Enter the address of the file where the message instruction will reside in memory In this case, binary file 1.

Enter the channel designation for the 1775-KA module. In this case, 2 is the module status, 5 is the 1775-KA module type, and 1 is the thumbwheel number of the module.

Enter the message type. This is always 1 for the 1775-KA module.

Key Strokes

SED [ENT]

IR [ENT]

-] [- B0:0/0 [ENT]

MSG [ENT]

FB1 [ENT]

E2.5.1 [ENT]

1 [ENT]

Allocating Memory

Editing Message Procedures

Enter a single 1775-KA assignment command or the name of a message procedure. In this case, the name of the message procedure is PROC_1.

End edits.

@PROC-1 [ENT]

EE [ENT]

Before the 1775–KA module can transfer data to or from any file in PLC–3 memory, that file must exist and it must have enough memory allocated to it to accommodate the data transfer. You can create and allocate a file using the PLC–3 memory management commands. Refer to the PLC–3 Programming Manual (publication 1775–801) for a description of memory management.

Table 5.B shows an example of editing a message procedure through an Industrial Terminal connected to a 1775–S4A module. Table 5.C shows how to edit the same message procedure through a data terminal connected to a 1775–S4B module.

52

Chapter 5

Table 5.B Example

System Prompt

ENTER SYMBOL STRING

ENTER SYSTEM ADDRESS OR SYMBOL

ENTER SYMBOL TYPE Enter the symbol type for the message

of Editing a Message Procedure Through an Industrial T

Action

Create the message procedure. In this case, MH1 mean Data Highway message procedure number 1.

Deleting existing null characters.

Enter message procedure commands. Note that you must use either an EXIT or a ST

OP command to end each procedure.

Insert the symbol definition for the name of the message procedure.

Enter the name of the message procedure. In this case, the name is PROC_1.

Enter the address where the message procedure is stored. In this case, the symbolic address MH1 can be used.

procedure name. This is always 2 for the 1775-KA module.

erminal

Key Strokes

ME, MH1, [ENT]

[DEL] [DEL] [DEL] [DEL]

(other commands) #H022$B0:5CC:1 [ENT] $B0:6=CC:1*2 [ENT] EXIT [ENT] [CANCEL CMD]

IS [ENT]

PROC_1 [ENT]

MH1 [ENT]

2 [ENT]

S4B>

<EOB>* *

S4B>

Table 5.C Example of Editing a Message Procedure Through a Data T

Enter the edit mode and create the message procedure name. Note that the 1775-S4B module automatically creates the symbol definition for the message procedure name.

Enter the insert mode of editing

Enter the message procedure command. Note that you must use either EXIT or ST

OP command to end each procedure.

Exit from the insert mode of editing.

Exit from the editing mode of the 1775-S4B module.

EDIT /H@PROC_1 [RET]

I [RET]

(other commands) #H022$B0:5=CC:1 [RET] $B0:6=CC:1*2 [RET] EXIT [RET]

[RET]

E [RET]

erminal

53

Chapter 5

Editing

Note that it is not always necessary to create a message procedure. If you want to execute just a single assignment command that is no more than 76 characters long, then you can enter that command as part of the ladder diagram message instruction (Table 5.A). If you want to execute more than one 1775–KA command, or if a single assignment command is more than 76 characters long, then you must create a message procedure to contain those commands.

Also note that every message procedure must end with either an EXIT or a STOP command. The EXIT command is normally preferred because the STOP command is a more extreme measure that results in error 179 (Appendix B).

54

Chapter

Message Procedure Commands

General

The 1775–KA module has its own command language that you can use in programming message procedures. This chapter describes the available commands and gives some examples on how to use them. Table 6.A summarizes the commands.

Table 6.A Message

Procedure Commands

Command

= (assignment)

CREATE

DELETE

(execute)

EXIT E

GOTO

ON_ERROR

STOP S

Format and Explanation

Assign a numeric value to a user symbol or copy data from the source to the destination

C@<system symbol><logical address>

Create a symbolic address and equate it to a logical address.

D @<system symbol>

Delete a symbolic address or an entire message procedure from PLC-3 memory

@<system symbol>

Execute the named message procedure.

erminate execution of the current message procedure.

G <label>

Continue executing the current procedure from the point specified by the label.

I <expression><embedded command>

Execute the embedded command only if the specified expression is true.

O <embedded command>3

Execute the embedded command only if an error occurs after this statement in the procedure.

erminate execution of the message (MSG) instruction in the

PLC-3 ladder diagram program.

Each command can be abbreviated to the letters shown in the format column of Table 6.A. In general, it is best to abbreviate a command to the shortest possible form. This not only makes the commands easier to program, but it also saves memory space and reduces execution time.

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Chapter 6

Message Procedure Commands

Blanks may be inserted anywhere to improve the readability of a message procedure. However, blanks should be kept to a minimum because they use memory space and slow execution of the message procedure.

Assignment Command

The assignment command is the most fundamental yet versatile of all the commands. Its primary purpose is to copy data from the source location to the destination location. Table 6.B lists the various types of sources and destinations. Any type of source in Table 6.B may be used with any type of destination listed.

Table 6.B

Source and Destination T

Data

Source

Direct V

alue

Procedural user symbol

Interprocedural user symbol

Logical address Logical address

Local symbolic address Local symbolic address

Global symbolic address Global symbolic address

Expression

ypes

Destination

Procedural user symbol (except when source is remote)

Interprocedural user symbol (except when source is remote)

62

Of special interest is the case where a user symbol is the destination of the assignment. In such a case, if the user symbol was not previously defined in the message procedure, a new symbol is generated. If the symbol has already been defined, using it again as a destination causes its value to be changed to the value given it by the latest assignment command.

Note that you can not transfer data from another station and place it into a user symbol defined at your local PLC–3.

Format

The equals sign (=) is the assignment command. As Table 6.A shows, the destination for the assignment is on the left of the equal sign, and the source or the numeric value is on the right. In all cases, the source value is assigned to (or copied to) the destination location. Thus, the assignment is from right to left on the command line. For example, the statement

$I12:024–US_5

Chapter 6

Message Procedure Commands

copies the value of user symbol US_5 into word 24 (octal) of input file

12.

Modifiers

Several modifiers may be added to the basic assignment command. These modifiers affect three aspects of the assignment:

Scope of assignment Priority level of Data Highway message Type of command message transmitted

Scope of Assignment

A double equals sign (==) can also be used for the assignment command. The extra equals sign modifies the scope of an assignment involving a user symbol. If the destination of the assignment is a user symbol, the double equals sign defines the destination to be an interprocedural user symbol. With the single equals sign, the destination becomes a procedural user symbol.

For example, the statement

US_2==6

defines US_2 to be an interprocedural user symbol and assigns to it the value 6.

Do not use the double equals sign (==) with anything other than a user symbol as the destination.

Message Priority

Data Highway messages may be either one of the following priority levels:

63

Chapter 6

Message Procedure Commands

Normal Priority

If you use the less–than sign (<) with the assignment command, the command will generate a priority Data Highway message. Without the less–than sign, the assignment command will generate a normal Data Highway message.

For example, the statement

#H027$I15:4<=$I12:24

transmits a priority message to Data Highway station 27 (octal).

The priority modifier can be used with either type of assignment (=or==).

Important: Stations with high priority messages are given priority over stations with normal priority messages throughout the command/reply cycle. For this reason, a command should be given a high priority designation only when special handling of specific data is required. Using an excessive number of high priority commands defeats the purpose of this feature and could delay or inhibit the transmission of normal priority messages.

Command Message Type

Command messages are of two types:

protected unprotected

As explained in section titled Data Transfers, (chapter 3), protected commands can access only specified areas of data table memory at a PLC/PLC–2 station. You will need to send a protected write command only if a switch at the remote PLC/PLC–2 prohibits other stations from sending unprotected write commands. Unprotected commands can access any area of the data table.

64

By default, command messages generated by the assignment command in PLC–3 message procedures are of the protected type. To generate an unprotected command message, use a blank space and the modifier U after the assignment command.

Chapter 6

Message Procedure Commands

For example, the command

#H027$0121=17407

would generate a protected write command to write the value 1740–7 into word 121 of Data Highway station 27. The command

#H027$0121=17407 U

would generate an unprotected command to do the same thing.

You may disable the transmission of unprotected commands through LIST options (section titled Module Options, chapter 2).

CREATE Command

The CREATE command generates a symbolic address and assigns it to a logical address. Table 6.A illustrates the format of the CREATE command. To create a local symbolic address, use the CREATE command by itself (the modifier/LOCAL is optional). To create a global symbolic address, use the modifier/GLOBAL after the CREATE command. In either case, the symbol has meaning only at the station where it was created.

The modifier/GLOBAL can be abbreviated to /G, and /LOCAL can be abbreviated to /L. For example, the statement

C/G @ TOTAL $E0.0.0.7

creates the global system symbol TOTAL to represent the logical address E0.0.0.7.

Note that this CREATE command for generating symbolic addresses should not be confused with the CREATE command for allocating file space in PLC–3 programming (Chapter 4).

DELETE Command

The DELETE command serves three main purposes:

Deleting message procedures from PLC–3 memory Deleting symbolic addresses Deleting interprocedural user symbols

65

Chapter 6

Message Procedure Commands

Using the DELETE command on a procedure name not only deletes the name but also erases the named procedure from PLC–3 memory. Using DELETE on a symbolic address or interprocedural user symbol merely deletes the symbol, but the data stored under that symbol remains intact.

Table 6.A shows the general format of the DELETE command. To delete a symbol or a procedure from the current context, use the DELETE command by itself (the modifier /LOCAL is optional). To delete a symbol or a procedure from all contexts, use the modifier/GLOBAL after the DELETE command.

The modifier /GLOBAL can be abbreviated to /G, and /LOCAL can be abbreviated to /L. For example, the statement

D/G @ PARTS_PGM

Execute

deletes the procedure PARTS_PGM from all contexts in PLC–3 memory.

Note that the /LOCAL modifier can be used on global system symbols. In such cases, the procedure or the symbol is deleted from the current context but can still be used in the other contexts.

To execute a message procedure, simply enter the delimiter @ followed by the procedure’s name. For example, the statement

@FIRST_PROC

causes execution of the procedure named FIRST_PROC.

Procedure names may be used anywhere that command can be used. In this way, one procedure can execute (call) another procedure. This allows for nesting of procedures. However, procedures may not be nested more than 3 layers deep.

EXIT Command

66

The EXIT command terminates execution of the current message procedure. If the current procedure was called (executed) by another procedure, the EXIT command returns control to the calling procedure. Control returns to the line following the execute statement.

Chapter 6

Message Procedure Commands

The format of the EXIT command is simply the single letter

Without any modifiers or parameters.

Each main procedure and nested procedure must end with either an EXIT command or a STOP command. The EXIT command is the preferred means of ending a procedure because the STOP command results in error 179 (Appendix B).

GOTO Command

The commands in a message procedure are normally executed sequentially. The GOTO command can change the order of execution.

Table 6.A illustrates the format of the GOTO command. Note that the parameter for a GOTO command is a label. Labels are signposts, or tags, that mark a location within the message procedure.

To generate a label, simply enter it on any one of the lines in a message procedure. The format for the label is

LABEL _A:

Nothing else may appear on the same line with the label. The label itself must conform to the same rules of construction as user symbols do. The trailing colon (:) is required when you first generate the label, but do not use the colon any other time you refer to the label.

When a GOTO command is encountered, execution of the message procedure resumes with the first command after the label specified in the GOTO. Note that you cannot use the GOTO command to jump from one procedure to another, even if the procedures are nested.

IF Command

The IF command makes logic decisions in the message procedure. Table

6.A shows the format of the IF command. The first parameter of the IF command is an expression (Chapter 4). The entire expression must be enclosed in a set of parentheses. The expression may be made as complex as desired through the use of multiple operators and nested expression.

The second element in the IF command is an embedded command. If the value of the expression is true (1), the embedded command is executed. If

67

Chapter 6

Message Procedure Commands

the value of the expression is false (0), the embedded command is not executed. The embedded command may be any of the available commands except another IF or an ON_ERROR.

Figure 6.1 demonstrates the combination of a label, a GOTO command, and an IF command to construct a simple loop that assigns the integers 0 through 7 to successive words in binary file 50.

Figure 6.1 Example

of Looping

NUM = 0

ON_ERROR Command

LOOP: $B50:(NUM) = NUM NUM = (NUM +1) IF (NUM .LE. 7) GOTO LOOP

10027-I

The ON_ERROR command specifies what action should be taken if an error is encountered during execution of the message procedure. The ON_ERROR command is not executed sequentially in the procedure; it is executed only when an error occurs.

Table 6.A illustrates the format of the ON_ERROR command. The ON_ERROR command contains an embedded command that is executed when an error occurs.

The ON_ERROR command applies to all other commands between itself and the next ON_ERROR command. For example, consider the following sequence:

68

Chapter 6

Message Procedure Commands

command line 1 command line 2 ON_ERROR GOTO RECOVER command line 3 command line 4 ON_ERROR ERR_CODE = $B2:16 command line 5

In this sequence, the first ON_ERROR command applies to command lines 3 and 4, while the second ON_ERROR command applies to command line 5.

Some command lines might not have an ON_ERROR command that applies to them. If an error occurs in such a command line,the procedure will stop executing.

STOP Command

Appendix B lists the error conditions.

The STOP command terminates execution of the MSG instruction in the PLC–3 ladder diagram program. This means that the STOP command stops execution of the current procedure and all procedures nested together with the current one.

The format of the STOP command is simply the single letter

without any modifiers or parameters.

The STOP command is a drastic means of terminating a message procedure, so it should be used only when no other action is possible. The normal means of terminating a procedure is the EXIT command (section titled EXIT Command). When the STOP command is used, it results in an error code of 179 (Appendix B).

Functions

In addition to containing commands and nested procedures, a message procedure can also contain functions. Functions can be used anywhere expressions can be used.

69

Chapter 6

Message Procedure Commands

There are two functions:

TO_BCD FROM_BCD

Figure 6.2 illustrates the format of these functions as they might appear in an assignment command.

Figure 6.2 Examples

of TO-BCD and FROM-BCD Functions

$D:12 = TO_BCD (27) COUNT = FROM_BCD ($D:12)

The parameter of the function must be enclosed in parentheses. The parameter may be any one of the following:

A direct numeric value (either decimal or octal) An expression A user symbol A logical address A symbolic address

Function Parameter

Function

Assignment Command

Destination of Resulting Value

10028–I

610

TO_BCD Function

The TO_BCD function converts its parameter into a binary coded decimal value that is 32 bits long. For example, the TO_BCD function in Figure 6.2 stores the number 27 in binary–coded–decimal format in word 12 of the decimal section of PLC–3 memory. After this function is executed, word 12 will contain the following bit pattern:

0000 0000 0010 0111

Chapter 6

Message Procedure Commands

FROM_BCD Function

The FROM_BCD function converts its parameter from binary–coded–decimal format to binary format. The resulting value is 32 bits long. For example, the FROM_BCD function in Figure 6.2 converts the contents of decimal word 12 from binary coded decimal to a regular decimal value of 27. From the above example (section titled TO_BCD Function), the FROM_BCD function stores the following bit pattern in user symbol COUNT:

0000 0000 0000 0000 0000 0000 0001 1011

As you can see from these examples, TO_BCD and FROM_BCD perform opposite functions.

Comments

You can add your own explanatory comments to any command line in a message procedure. To do this, enter a semicolon (;) after the command. Then enter your comment after the semicolon. Figure 6.3 illustrates the format for comments.

Figure 6.3

for Comments

Format

COUNT = 0 ; INITIALIZE COUNTER

Anything that appears between a semicolon and the end of the command line is considered to be a comment. Comments may be any length. The end of the command line, and therefore the end of your comment, is delimited by the carriage– return and line–feed pair of characters.

Comment

Comment Delimiter

Command

10029–I

A comment can be the only thing on a line. Do not use comments on the same line as label. Doing so will cause errors in the message procedure.

611

Error Reporting

Chapter

General

Reporting Error Codes

Recovery from Errors

The 1775–KA module detects and reports various types of errors. Appendix B lists all the errors reported by the module. As you can see from the appendix, some of the error codes relate to communications over the Data Highway, while others relate to programming errors in the message procedures.

The 1775–KA module reports errors by their code numbers. The module stores the error code in the interprocedural user symbol ERROR. The symbol ERROR should be reserved exclusively for error reporting by the module, so do not use this symbol for any other purpose.

ERROR contains only the last error encountered during execution of a command or message procedure. If you want to save the error code or manipulate it in any way, use an assignment command to copy the code into a more permanent storage word.

Unless you specify differently, the 1775–KA module will stop executing the current message procedure as soon as the module detects an error. To specify a different action, use the ON_ERROR command in the message procedure. Then, when the module encounters an error, it will perform the action specified in the nearest preceding ON_ERROR command. After the module is done performing the ON_ERROR action, it will resume executing the message procedure at the next command line after the one in which the error occurred.

For example, a message procedure can contain the command

ON_ERROR @ RECOVER

When an error occurs in the procedure, the above command will cause the 1775–KA module to execute the procedure named RECOVER. The procedure RECOVER might be a routine for monitoring error codes. After executing RECOVER, the module will resume executing the original procedure at the next command line following the one in which the error occurred.

71

Chapter 7

Error Reporting

Error Monitoring

To aid in error monitoring, the 1775–KA module maintains a 6–word error block in the module status area of PLC–3 memory. This error block contains the following information:

Word 0 – error code for the last error that occurred in the current message procedure

Word 1 – total number of errors that occurred in the current message procedure

Word 2 – always contains the value 1

Word 3 – line number where the error occurred in the highest level (nest level 1) message procedure

Word 4 – line number where the error occurred in the next highest level (nest level 2) message procedure

Word 5 – line number where the error occurred in the lowest level (nest level 3) message procedure

The error codes reported are those listed in Appendix B.

The line number is the relative location of a command line from the beginning of the message procedure containing the line. The first line of each procedure is line number 1, and any following lines are numbered in ascending sequence. Nested procedures begin with line 1 again, thus the need for words 3, 4, and 5 in the error block.

You do not enter the line numbers for a procedure; the 1775–KA module automatically keeps track of the line numbers for you. The line numbers do not appear in a listing of the message procedure, but they are recorded internally by the module.

Error Block Operation

Figure 7.1 illustrates how the error block works. In this figure, an addressing error (invalid destination address) occurs in procedure SUB2, which is nested 3 levels deep. Word 5 of the error block gives the line number where the error occurred in procedure SUB2. Word 4 gives the number of the line in procedure SUB1 that executed procedure SUB2.

72

Chapter 7

Error Reporting

And word 3 gives the number of the line in procedure MAIN that executed procedure SUB1.

Line Number

150

MAIN

SUB 1

Figure 7.1 Examples

of Error Block Operation

Procedure Word

•

@SUB 1

•

@SUB 2

•

Error Block Contents (decimal)

124

150

SUB 2

•

6:12 = COUNT

•

10030–I

73

Chapter 7

Error Reporting

Note that an ON_ERROR or an IF command may contain an embedded command to execute another procedure. In these cases, the embedded execute command is treated just like a nesting level. Figure 7.2 illustrates this point for an ON_ERROR command. In this figure, an addressing error in line 10 of procedure MAIN causes activation of the ON_ERROR command, which calls for execution of procedure SAM. But SAM also contains an error. The error in SAM is the last one detected, so it is the one finally reported in the error block. Since procedure SAM is called by the ON_ERROR command in procedure MAIN, the nesting for SAM is 2 levels deep.

Figure 7.2 Examples

Line Number Procedure Word

MAIN

ON_ERROR @SAM

•

of ON_ERROR Nesting

•

7.2 = 1000

•

SAM

•

$25:0 = N

•

Error Block

Contents (decimal)

160

74

10031–I

Chapter 7

Error Reporting

Access to Error Block

The error block retains its data even after the message procedures are done executing. It is re–initialized with each execution of a MSG instruction in the PLC–3 ladder diagram program.

The extended address for the beginning of the error block file is

$E2.5.nn.4.0.

where “nn” is the thumbwheel number of the 1775–KA module. You can access this error block by any one of the following means:

Displaying it through the front panel of the PLC–3 controller Using the data monitor mode of the Industrial Terminal (cat. no.

1770–T4)

Using the move status (MVS) command in the PLC–3 ladder diagram

program Using the I/O Scanner–Message Handling Module (cat. no. 1775–S4B) Using the 1775–KA module Using the 1775–GA

75

Programming Examples

Chapter

General

Individual Commands

I0012

This chapter presents some detailed examples of 1775–KA module commands and message procedures.

The first set of examples shows individual commands that could be programmed directly into a PLC–3 message (MSG) instruction. Figure

8.1 illustrates the differences in reading and writing data between two PLC–3 stations. Figure 8.2 shows how to write different types of data to a remote PLC–3 station. Figure 8.3 shows how to write different types of data to a remote PLC or PLC–2 station.

Figure 8.1 Reading

Reading word 5 of binary file 3 at data highway station 045 into word 17 of integer file 4.

and W

riting PLC-3 Data W

ord

MSG

MESSAGE TYPE 1 CTL = FB200:0000=200 CHANNEL: E2.5.1 $NA:17=#H045 $B3:5

STAT

DN 15

STAT

ER 13

I0012

Destination (local)

Writing word 5 of binary file 3 into word 17 of integer file 4 at data highway station 045.

MSG

MESSAGE TYPE 1 CTL = FB200:0001=200 CHANNEL: E2.5.1 #H045=N4:17 $B3:5

Destination

(remote)

Source (remote)

Source

(local)

STAT

DN 15

STAT

ER 13

10032-I

81

Chapter 8

Programming Examples

Data Type Assignment Statement

File #H045$N4 = $B3

Figure 8.2

Data to a Remote PLC-3 Station

Writing

Destination file must be exactly the same size as source file.

Word range

Word #H045$N4:17 = $B3:5

Bit #H045$N4:17/5 = $B3:5/13

#H045$N4:17 = $B3:5,20

Destination file must be large enough to accept full range being transferred.

20 words starting at word 5 of binary file 3

Decimal bit numbers

10033-I

82

Figure 8.3

riting Data to a Remote PLC/PLC-2 Station

Data Type Assignment Statement

File #H021$040 = $B3

Destination PLC/PLC–2 file must be at least as large as source PLC–3 file.

Chapter 8

Programming Examples

Word range

Word #H021$040 = $B3:5/13

Bit #H021$040/5 = $B3:5/13

Priority Write

Unprotected Write ––

(refer to publication 1771–802 or 1774–6.5.8.)

affected by switch settings at remote PLC/PLC–2 station

#H021$040 = $B3:5,20

Destination file must be large enough to accept all words being transferred.

#H021$040 <= $B3:5

20 words starting at word 5 of binary file 3

Decimal bit numbers

Priority assignment command

#H021$040 = $B3:5 U Unprotected command

Space required

10034-I

83

Chapter 8

Programming Examples

Message Procedure

Figure 8.4 presents a printed listing of a Data Highway message procedure. As the listing indicates, the purpose of the procedure is to monitor the state of a status bit in a remote Data Highway station.

Figure 8.4 Example

; PROCEDURE –– @REM_TURNON

; This procedure will monitor the state of a bit in a remote ; station and, when that bit goes true, turn on a bit ; locally for either 300 seconds or until the remote bit ; goes false. ;

ON_ERROR @LOG_ERROR A = = 0 CREATE @TIM–START $B0:0 CREATE @TIM_CTL $TCTL:1 CREATE @TIM_PRE $TPRE:1 T_ON_BIT = 0 T_DONE_BIT = 017 CREATE @PROCESS $N3:7 P_ON_BIT = 5 ON = 1 OFF = 0 LOOP 1: B0:0/1 = $H023$B5:3/2 IF ($B0:0/1 .EQ. OF) GOTO LOOP1 @TIM_PRE = 300 @TIM_START/T_ON_BIT = ON @PROCESS/P_ON_BIT = ON LOOP 2: $B0:0/1 = $H023$B:3/2 IF (($B0:0/1 .EQ. ON) .AND. (@TIM_CTL/T_DONE_BIT .EQ. OFF)) GOTO LOOP2 @PROCESS/P_ON_BIT = OFF

EXIT ; PROCEDURE –– @LOG_ERROR ;This procedure will fetch the error block out of the

; Module Status Area and record it along with the time ; of day in status file 5. ; CREATE @STATUS $S5 CREATE @ERR_BLK $E2.5.1.4.0 CREATE @TOD $S1:3 @STATUS: (A) = @ERR_BLK,6 @STATUS: (A + 6) = @TOD,2 IF ((ERROR .GE. 81) .AND. (ERROR .LE. 92)) GOTO NO_STN :no station – fatal error IF (A .GE. 72) GOTO TIMEOUT A = = A + 8 EXIT ; NO_STN: $S4:3/5 = 1 STOP ; TIMEOUT: $54:3/4 = 1 EXIT

Data Highway Message Procedure

;log errors and time of day ;initialize error pointer ;timer start word ;timer control word ;timer preset word ;timer on bit ;timer done bit ;process word ;process on bit

;check remote bit in loop ;fetch and save remote bit

;set timer for 300 sec ;turn timer on ;turn process on ;check timer and remote bit in loop ;fetch and save remote bit

;copy error block (6 words) ;copy time of day (hrs, mins)

;after ten errors, tell operator

;energize 1775–S4B report generation rung ;exit procedure with an error

;energize 1775–S4B report generation rung ;return to @PREM_TURNON

10035-I

84

Chapter 8

Programming Examples

Some of the statements in the sample procedure are not necessary to accomplish the bit monitoring. However, they were included to illustrate more of the functions and programming techniques available with the 1775–KA module.

Note that the 300 second timer used in this example is not an accurate, real– time clock. This is because the time between successive executions of the bit/timer check depends on Data Highway activity and on the activity of the local PLC–3 processor. For example, if the 300 second timer times out immediately after its done bit is checked, the 1775–KA module will not detect this condition until its next pass through LOOP2. If the Data Highway is busy with other activity, it will take a while for LOOP2 to check the remote bit. PLC–3 ladder diagram programming provides better timer updates and responses.

The example procedure also assumes that the referenced memory areas have been created. Specifically:

1. Status file S5 must be big enough to hold a reasonable number of

timeout errors (error #37).

2. Timer T1 is a one–second timebase timer. Bit B0:0/0 controls the

ladder diagram rung that activates the timer. Figure 8.4 refers to this bit as TIM_START/T_ON–BIT.

3. Bit S4:3/4 activates a message instruction that executes a report

generation procedure. In this way, the 1775–KA module can indirectly cause execution of a report generation procedure to display a message on the operator’s terminal.

85

Chapter

Computer to PC Communication

Introduction to Layered Communication

This chapter and the chapters that follow (10,11, and 12) described how to write a software driver that enables your computer to communicate through the RS–232–C port of the PLC–3 Communication Adapter Module. Therefore, you do not need to read these chapters if you are only using PC’s. The interface modules contain software drivers for PC to PC communication.

In this chapter and the chapters that follow (10,11, and 12) we describe a layered approach to writing a software driver for your computer. According to the standard for network architecture developed by the International Standards Organization (ISO), communication networks should be divided into layers. Each layer performs specific functions. By separating the communication network into independent layers, it is easier to make changes to one of the network’s functions without having to redesign the entire network. Ideally, the layers of a network should be as independent of one another and interact with one another in the same way as the organs of the human body. Because the organs of the human body are independent of one another, it’s possible for a surgeon to operate on the lungs or heart without losing the life of the patient. Yet at the same time the organs of the body interact when we run or walk or type on a word processor.

You should use a layered approach to developing communication software for your computer. You don’t have to design your communication software in this layered fashion, but your software must perform all the functions described for the layers in this manual. In most cases, it will be easier for you to implement and debug the communication software if you follow this layered approach.

The Data Highway uses these four layers of the ISO model for communication between stations:

application layer – provides the Data Highway commands that you use

to transfer data and manage the network.

network layer – determines how you address a Data Highway

command. It also provides less visible functions, such as controlling the flow of information, establishing a path between stations, and routing messages from your station to another station.

91

Rockwell Automation 1775-KA User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Table of Contents

General

About This Manual

Module Description

Specifications

Applications

General

Hardware Installation

Programmable Configuration Parameters

Backup Configurations

General

Some Terminology

Levels of Programming

Data Transfers

General

Number Systems

Addresses

Symbols

PLC-3 Address Specifications

PLC/PLC-2 Address Specifications

Remote Station Address Specifications

Expression

General

Editing the Message Instruction

Allocating Memory

Editing Message Procedures

General

Assignment Command

CREATE Command

DELETE Command

Execute

EXIT Command

GOTO Command

IF Command

ON_ERROR Command

STOP Command

Functions

Comments

General

Reporting Error Codes

Recovery from Errors

Error Monitoring

General

Individual Commands

Message Procedure

Introduction to Layered Communication