Rockwell Automation 1770-KF2 User Manual

Data Highway or Data Highway Plus Asynchronous (RS-232-C or RS-422-A) Interface Module

Cat. No. 1770-KF2)

User Manual

Important User Information	Because of the variety of uses for the products described in this publication,
	those responsible for the application and use of this control equipment must
	satisfy themselves that all necessary steps have been taken to assure that each
	application and use meets all performance and safety requirements, including
	any applicable laws, regulations, codes and standards.
	The illustrations, charts, sample programs and layout examples shown in this
	guide are intended solely for purposes of example. Since there are many
	variables and requirements associated with any particular installation, the
	Allen-Bradley Company, Inc. does not assume responsibility or liability (to
	include intellectual property liability) for actual use based upon the examples
	shown in this publication.
	Allen-Bradley Publication SGI-1.1, ªSafety Guidelines for the Application,
	Installation and Maintenance of Solid State Controlº (available from your local
	Allen-Bradley office) describes some important differences between solid-state
	equipment and electromechanical devices which should be taken into
	consideration when applying products such as those described in this
	publication.
	Reproduction of the contents of this copyrighted manual, in whole or in part,
	without written permission of the Allen-Bradley Company Inc. is prohibited.
	Throughout this manual we use notes to make you aware of safety
	considerations:
	ATTENTION: Identifies information about practices or
	circumstances that can lead to personal injury or death, property
	damage or economic loss.
	Attentions help you:
	identify a hazard
	avoid the hazard
	recognize the consequences
	Important: Identifies information that is especially important for
	successful application and understanding of the product.
	Interchange, ControlView, Data Highway Plus and DH+ are trademarks and PLC is a registered
	trademark of Allen-Bradley Company, Inc.
	HART is a registered trademark of Rosemount Inc.
	IBM is a registered trademark of International Business Machines Corporation.

Table of Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	1 1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1 1
About This Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1 1
Module Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1 3
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1 4
Data Highway Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1 5
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .PCL Applications		1 7

Communication Concepts . . . . . . . . . . . . . . . . . . . . . . . . .	2 1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		2 1
Physical Link Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		2 2
Software Layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		2 8

Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		3 1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			3 1
. . . . . . . . . . . . . . . . . . . . . . . . .Communication Option Switches			3 1
Mounting (Placing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			3 8
Interface Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			3 9
Diagnostic Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	3 18

Asynchronous Link Protocols . . . . . . . . . . . . . . . . . . . . . .		4 1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			4 1
Definition of Link Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			4 1
Full Duplex Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			4 2
Half Duplex Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	4 21

Message Packet Formats . . . . . . . . . . . . . . . . . . . . . . . . . .	5 1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		5 1
Application Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		5 1
Network Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		5 1
Message Packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		5 3
Message Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		5 7

Data Encoding and Addressing . . . . . . . . . . . . . . . . . . . . .	6 1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		6 1
Data Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		6 1
Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		6 8

ii	Table of Contents

Error Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		7 1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	7 1
ERROR WORD in User Programming
(1771 KG, 1771 KA, 1771 KA2, 1774 KA Modules) . . . . . . . . .			7 2
Error Codes for 1775 KA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			7 8
Internal Error Counters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	7 19

Switch Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		A 1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		A 1
Message Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		B 1
General Asynchronous Link Error Codes (STS, EXT STS) .		C 1
Where to Find Asynchronous Link Error Codes . . . . . . . . . . . . . . .		C 1
The STS Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		C 1
The EXT STS Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		C 3
Detailed Flowcharts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		D 1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		D 1
Data Link Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		E 1
Data Link Layer Operation on Data Highway . . . . . . . . . . . . . . . . .		E 1
Floating Master . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		E 1
Message Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		E 3
Polling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		E 3
Data Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		E 4
Link Disconnect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		E 5

Chapter 1

Introduction

General	A 1770-KF2 Series B module is a communication interface that links
	intelligent RS-232-C or RS-422-A (asynchronous) devices to an
	Allen-Bradley local area network. By setting switches on the KF2, and
	changing cables, you can direct communications over a Data Highway or
	a Peer Communication Link (PCL). With a 1770-KF2 module, a
	computer on a PCL can communicate with any PLC-5 node on the
	network. Other current Allen-Bradley products that communicate over a
	PCL are the 1784-T50 Industrial Terminal System and the 1785-KA
	Communication Adapter Module.
	The KF2 is designed to operate in a control-room environment on a
	tabletop. It takes its power from an AC wall outlet, and it gives you a
	choice of full-duplex or half-duplex protocol on its asynchronous link.
	The module has Data Highway compatibility, and it supports all PCL
	facilities except internetworking.
	(Internetworking would indicate that a computer on a PCL could talk to a
	node on another PCL, or to a station on a Data Highway link. That may
	be possible in the future, but it isn't right now. A computer on a Data
	Highway, though, using a 1770-KF2 and a 1785-KA can communicate
	with PLC-5s on a PCL.)
About This Manual	This manual describes installation, operation, and communication
	protocols of a 1770-KF2 module; and it assumes that you are already
	thoroughly familiar with how to program your computer or other
	intelligent asynchronous device. It does not assume prior knowledge of
	the Allen-Bradley Data Highway or a Peer Communication Link.
	Table 1.A lists related documentation that might be helpful in conjunction
	with this manual. For more details about the programming and operation
	of specific Allen-Bradley programmable controllers, refer to the
	appropriate user's manual for that controller.

1-1

Chapter 1

Introduction

Table 1.A

Related Documentation

Publication	Old Publication	Title
Number	Number
1770-6.2.1	1770-810	Data Highway Cable Assembly and Installation
		Manual
1771-6.5.1	1771-801	Communication Adapter Module
		(Cat. No. 1771-KA2) User's Manual
1771-6.5.15	1771-822	Communication Controller Module
		(Cat. Nos. 1771-KE, -KF) User's Manual
1771-6.5.8	1771-811	PLC-2 Family/RS-232-C Interface Module
		(Cat. No. 1771-KG) User's Manual
1775-6.5.1	1775-802	PLC-3 Communication Adapter Module
		(Cat. No. 1775-KA) User's Manual
1773-6.5.2	1773-801	PLC-4 Communication Interface Module
		(Cat. No. 1773-KA) User's Guide
1785-6.8.1		PLC-5/15 Processor Manual
1785-6.6.1		PLC-5/15 Assembly & Installation Manual
6226-6.5.1		Industrial Terminal Support Software System
		Manual
1784-6.5.1		Industrial Terminal (1784-T50) User's Manual
1785-6.5.1		PCL-to-Data Highway Communication Adapter
		Module (1785-KA) User's Manual

This manual is organized as follows:

Chapter 2 Ð Explains basic communication concepts. Chapter 3 Ð Tells how to install a KF2 module.

Chapters 4, 5, and 6 Ð Describe the communication protocol used by a KF2 module.

Chapter 7 Ð Summarizes error reporting.

1-2

Chapter 1

Introduction

Module Description

Figure 1.1 shows the 1770-KF2 module's hardware features:

Diagnostic Indicators

Connectors for Data Highway and RS-232-C Devices

Communication Option Switches

On/Off Switch, Power Plug, Fuse, and Voltage Select Switch

Figure 1.1

1770-KF2 Communication Interface Module

ALLEN±BRADLEY

PWR	XMTG RCVG RDY ACTV CPU

DATA HIGHWAY

COMMUNICATION INTERFACE

A KF2 also features extensive self-diagnostics. At power-up, tests are run on internal memory, timers, and firmware integrity. Any failure causes the red front-panel CPU indicator to flash. Also, the module continuously checks the memory and firmware during operation.

1-3

Chapter 1

Introduction

Specifications	Table 1.B lists KF2 module specifications.
	Table 1.B
	KF2 Module Specifications
	Specification		Requirements
	Communication Rates	•	Data Highway: 57,600 bits per second (recommended)
		• Peer Communication Link: 57,600 bits per second
			(recommended)
		• Asynchronous: Switch selectable from 110 to 9.600 bits
			per second
	Functions	•	Interface a programmable RS-232-C or RS-422-A
			compatible device with an Allen-Bradley Data Highway.
		• Serve as a replacement for a 1771-KD Communication
			Controller Module.
	Location	•	Tabletop (or other horizontal surface)
		• Controlled environment, e.g., office or control room
	Communication Ports	•	Data Highway: 15-pin male EIA D-connector
		• Peer Communication Link: 15-pin male EIA
			D-connector
		• Data Highway Monitor: 9-pin female EIA D-connector
		•	Asynchronous (RS-232-C/RS-422-A): 25-pin male
			EIA D-connector
	Cabling	•	Data Highway: Data Highway Dropline Cable
			(Cat. No. 1770-CD)
		• Asynchronous RS-232-C: User-Supplied Data
			Terminal Interface Cable or Modem Interface Cable
		• Asynchronous RS-422-A: User-Supplied Data Terminal
			Interface Cable
	Power Requirements	•	Selectable: 115 V/60 Hz or 230 V/50 Hz
		•	Watts: 3.5
	Ambient Temperature	•	32oF to 113oF (0oC to 45oC) Operational
	Rating	•	-40oF to 185oF (-40oC to 85oC) Storage
	Ambient Humidity Rating	•	10% to 80% Non-Condensing
	Physical	•	Size: 10-3/8 in. x 10.0 in. x 3-3/8 in. (263.5 mm x
			254 mm x 85.7 mm)
		• Weight: 6.0 pounds (2.7 Kg)

1-4

Chapter 1

Introduction

Data Highway Applications	A KF2 module provides either a point-to-point link or a multi-drop link
	between an Allen-Bradley Data Highway and an intelligent asynchronous
	device. By ªintelligent asynchronous deviceº we mean any device that
	complies with RS-232-C or RS-422-A electrical standards and that can be
	programmed to handle the communication protocol described in
	Chapters 4 through 6 of this manual. Throughout this manual, we will
	also use the term ªcomputerº in a general sense to refer to this type of
	device. Some examples include:
		An Allen-Bradley Advisor 2+TM Color Graphic System
		A PLC-3 Programmable Controller and Connected Communication
		Adapter Module (Cat. No. 1775-KA)
		A PLC-2 Family Programmable Controller and Connected PLC-2
		Family/RS-232-C Interface Module (Cat. No. 1771-KG)
		A PLC-4 Microtrol Programmable Controller and Connected
		Communication Interface Module (Cat. No. 1773-KA)
		A Variety of Minicomputers and Microcomputers
	In point-to-point configuration, the KF2 module connects one intelligent
	asynchronous device as a single station on a Data Highway. Figure 1.2
	illustrates this configuration. Point-to-point links can use either peer-to-
	peer (full-duplex) or master-slave (half-duplex) communication.
	Figure 1.2
	Point-to-Point Links
		Computer
		Modem
				Modem Link
						Computer
		Modem		Asynchronous Link
				(50 Cable-Ft. Max.)
		KF2 Module				KF2 Module

KF2 Module

Allen±Bradley Longline

RS-232-C Link Data Highway Link

(7,000 Cable-Ft. Max.)

1771-KG

Module

PLC-2/30

Processor

11687

1-5

Chapter 1

Introduction

In a multi-drop configuration, one intelligent asynchronous device connects to several Data Highways through sets of modems and KF2 modules. Figure 1.3 illustrates this type of configuration. If the multi-drop link consists of broadband modems, you can select either peer-to-peer (full-duplex) or master-slave (half-duplex) communication. If the multi-drop link consists of baseband modems, you must use master-slave (half-duplex) communication because baseband modems support only one communication channel.

Figure 1.3

Multi-Drop Link

Computer

Modem

Multi-Drop Modem Link

Modem

Modem

KF2 Module

1771-KG

Module

Data Highway Link

PLC-2/15

Processor

1775-KA

1773-KA

Modem

Module

Module

PLC-3

PLC-4

Microtrol

Processor

Processor

KF2 Module

Data Highway Link

KF2 Module

1771-KA

1774-KA

Module

Module

PLC-2

PLC

Computer

Processor

Processor

11688

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Chapter 1

Introduction

In either type of configuration, there are three possible ways you can connect a KF2 module:

Direct connection to an intelligent asynchronous device if the KF2 module is mounted within 50 cable-feet of an RS-232-C, or within 4,000 cable-feet of an RS-422-A device.

Direct connection to an Allen-Bradley 1775-KA, 1773-KA, or 1771-KG interface module if the KF2 module is within 50 cable-feet of the other module.

Modem connection if the KF2 module is within 50 cable-feet of an RS-232-C compatible modem, or within 4,000 cable-feet of an RS-422-A device.

	You can also use the 1770-KF2 module to replace a 1771-KD module in
	an existing application. By properly setting the option switches on the
	KF2 module, you can make this replacement without having to change
	any application programs that you were using with the 1771-KD module.
	Refer to Chapter 3 under ªReplacing a 1771-KD Module with a KF2
	Moduleº for switch settings.
PCL Applications	A 1770-KF2 Series B module provides either a point-to-point or
	multi-drop link between an Allen-Bradley Peer Communication Link
	(PCL) and an intelligent asynchronous device. You can use a PCL link
	when you have a small number of PLC-5/15 stations in a local cluster.
	Typically, a PCL link connects PLC-5/15s that need to communicate with
	each other frequently. If your system requires more than ten stations,
	consider breaking it into smaller PCL links connected by a Data Highway
	to optimize performance.
	The KF2 Series B module provides an interface between either:
	an RS-232-C or RS-422-A asynchronous link to Data Highway, or
	an RS-232-C or RS-422-A asynchronous link to a PCL network as
	shown in Figure 1.4.

1-7

Chapter 1

Introduction

Figure 1.4

A PCL Network Connected to a Data Highway

Advisor 2+TM

PLC-3

1770-KF2

1775-KA

Data Highway

1785-KA

PCL

PLC-5

PLC-5

1770-KF2

Computer

14690

Important: A 1770-KF2 module on a PCL link cannot access a station on the Data Highway through a 1785-KA module. A KF2 module on the Data Highway, however, can access a station on a PCL link through a 1785-KA.

1-8

Chapter 2

Communication Concepts

General	This chapter presents some of the concepts of communication with the
	KF2 module. It describes the physical communication links to the module
	and the various levels of software necessary to make those links work.
	A KF2 module connects a computer or programmable controller to an
	Allen-Bradley local area network (LAN), either Data Highway or Peer
	Communication Link (PCL). In doing so, the module acts as an interface
	between two physical communication links:
	Data Highway or PCL, Called ªNetwork Linkº
	RS-232-C or RS-422-A, Called ªAsynchronous Linkº
	A Data Highway network provides peer-to-peer communication between
	the KF2 module and other stations on the Data Highway. It uses a
	half-duplex (polled) protocol and rotation of link mastership.
	A Peer Communication Link provides peer-to-peer communication
	between the KF2 module and other stations on the PCL. The PCL uses
	token-passing to control access to the link.
	The asynchronous link can provide either peer-to-peer communication
	through a full-duplex (unpolled) protocol, or master-slave communication
	through a half-duplex (polled) protocol.
	In addition to a physical link layer, communication on either the network
	link or the asynchronous link involves three levels of software:
	Application Layer
	Network Layer
	Data Link Layer
	If you are using a computer on an asynchronous link, you must program
	all three layers. For A-B programmable controllers, you need program
	only the application layer; the Data Highway interface modules (or for the
	PCL, the PLC-5 itself) automatically take care of the other two layers.
	The rest of this chapter presents some of the concepts behind the physical
	communication links and their three software layers. For more details on

2-1

Chapter 2

Communication Concepts

	the application and network layers, refer to Chapters 5 and 6. For more
	on the data link layer of the asynchronous link, refer to Chapter 4 and
	Appendix D.
Physical Link Layer	The physical link layer is a set of cables and interface modules that work
	together to provide a channel for communication between the various
	points, called stations, on the physical link. A station consists of an
	intelligent programmable device (e.g., PC or computer) and the module or
	modules that interface it with the physical link.
	In this way, the KF2 module allows stations on one link to communicate
	with stations on the other link. Since these two physical links have
	different communication protocols, the KF2 module serves mainly as a
	protocol translator.
	Data Highway
	The Data Highway and the PCL are both local area networks (LANS) that
	allow peer-to-peer communication among up to 64 stations. Figure 2.1
	illustrates a Data Highway network.
	The Data Highway link consists of a trunkline that can be up to
	10,000 feet long and droplines that can be up to 100 feet each. Each
	station is at the end of a dropline.
	A Data Highway link implements peer-to-peer communication through a
	modified token-passing scheme called the floating master. With this
	arrangement, each station has equal access to become the master. The
	stations bid for temporary mastership based on their need to send
	information.
	Unlike a master/slave relationship, a floating master relationship does not
	require the current master to poll each station to grant permission to
	transmit. Therefore, it provides a more efficient network because there is
	less overhead per transaction.

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Chapter 2

Communication Concepts

Figure 2.1

Data Highway Network

PLC-3
		Computer
Processor
1775-KA						Advisor 2+TM
Module
		MODEM
				MODEM				RS-232-C Link
								50 Cable-Ft. Max.
				Link
		MODEM
						1770-KF2
						Module
		1770-KF2
		Module							Data
									Highway
									Link

						1770-KF2
						Module
					RS-232-C Link
					50 Cable-Ft. Max.
1771-KA			1773-KA			1771-KG
Module			Module			Module
PLC-2/15			PLC-4			PLC-2/30
Processor			Loop			Processor

11299A

Stations

A station consists of a computer or PC processor and the module or modules that interface it with the Data Highway link. Within a station that contains a KF2 module, an asynchronous link is required as an auxiliary link to the network. Figure 2.1 shows three such stations.

2-3

Chapter 2

Communication Concepts

One station consists of an Advisor 2+TM Color Graphic System connected to a KF2 module through an RS-232-C link limited to 50 cable-feet. Another station consists of a computer interfacing with a KF2 module through a modem link that is limited only by the nature of the modems themselves.

The third such station consists of a 1771-KG module interfacing a PLC-2/30 processor with a KF2 module through an RS-232-C link limited to 50 cable-feet. If you want a link longer than 50 cable-feet, you can use modems.

PC Programming

All Allen-Bradley PC processors can be connected to a Data Highway through an appropriate station interface module. All of these processors can receive and reply to command messages, and some of them can also transmit command messages. For an explanation of how to program PCs to send and receive messages, refer to the user's manual for the appropriate station interface module.

Computer Programming

The communication protocol for the Data Highway link is transparent to a computer on the network. However, for a computer to send or receive messages through the Data Highway network, it must be programmed to communicate with its KF2 module over an asynchronous link.

Chapters 4, 5, and 6 describe the protocol that you must program your computer to use on such an asynchronous link.

Peer Communication Link

A PCL has much the same topology as the Data Highway, described in the previous chapter; but it is designed for fewer, closely coupled, PCs. The PCL implements peer-to-peer communication with a token-passing scheme to rotate link mastership among the stations connected to that link. Since such a method does not require any polling, it is very time efficient. The PCL also uses timeouts to recover from any fault that disables the station that has the token.

2-4

Chapter 2

Communication Concepts

Stations

A station consists of a computer, or PC processor, and the module or modules that interface it with the PCL. Within a station that contains a KF2 module, an asynchronous link is required as an auxiliary link to the network. PCL networks currently use PLC-5 processors, which interface directly to the PCL; and no station interface module is required. You can, however, connect other PCs, as shown in Figure 2.2.

Figure 2.2

PCL Network Connected to Various PC Processors

PLC-4			PLC-3			PLC-2/30
Loop			Processor			Processor
1773-KA			1775-KA			1771-KG
Module			Module			Module

KF2		KF2		KF2
Module		Module		Module

PCL

11300A

Other PCL stations can be computers that interface with the KF2 module either directly or through a modem link, or a PCL-to-Data Highway communication adapter (1785-KA), which you can use to connect a PCL to the Data Highway.

PC Programming

All Allen-Bradley PC processors can receive command messages and reply to them, and some can transmit commands. For an explanation of how to program PCs to send and receive messages, refer to the user's manual for that particular station interface module or, in the case of a PLC-5, the processor itself.

2-5

Chapter 2

Communication Concepts

Computer Programming

The communication protocol for the PCL is transparent to a computer on the network. However, for a computer to send or receive messages through the PCL, it must be programmed to communicate with its KF2 module over an asynchronous link. Chapters 4, 5, and 6 describe the protocol that you must program your computer to use on this link.

Configuration Selection

Figure 2.1 and Figure 2.2 illustrate configurations in which PC stations can communicate with each other and with computers through network ports and asynchronous ports on the station interface modules. Each configuration is useful, depending on your application.

If you want to provide a peer-to-peer communication among many PCs and/or a computer, use a Data Highway network as shown in Figure 2.1. For communication among a small cluster of PCs and a computer, use a PCL as shown in Figure 1.4. For distances longer than the networks provide, you can use an auxiliary longline asynchronous (RS-232-C or RS-422-A) link or a modem link.

A Data Highway link has a communication rate of 57,600 bits per second and a half-duplex (peer-to-peer, polled) protocol. A KF2 asynchronous link is selectable RS-232-C/RS-422-A and has a selectable communication rate up to 9,600 bits per second. It uses a selectable protocol of half-duplex (master-slave polled) or full-duplex (peer-to-peer, unpolled).

A master-slave communication protocol can be selected for any link to a computer. A peer-to-peer communication protocol can be selected only for a point-to-point link or a broadband modem multi-drop link to a computer.

Even with only two stations, you may want a Data Highway or a Peer Communication Link. Either network provides the flexibility of easy reconfiguration or expansion if you want to be able to add more stations later, and it also provides more error checking than an asynchronous link.

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Configuration Considerations

Allen-Bradley manufactures a variety of communication interface modules for different applications:

		Communication Interface Module	Cat. No.	Note
	PLC Communication Adapter Module		1774-KA	1
	PLC-2	Family Communication Adapter Module	1771-KA2	1
	PLC-3	Communication Adapter Module	1775-KA
				1 & 2
	PLC-4	Communication Interface Module	1773-KA
				1 & 2
	PLC-5/Data Highway Communication Adapter Module		1785-KA
				±±
	PLC-2	Family/RS-232-C Interface Module	1771-KG
				2
	Communication Controller Modules		1771-KE, -KF
				3
	Communication Interface Module		1770-KF2B
				3
	Provides interface between:

1A PC Processor and a Data Highway Communication Link

2A PC Processor and an RS-232-C Communication Link

3A RS-232-C Communication Link and a Data Highway Communication Link

A 1785-KA module interfaces a Data Highway with a Peer Communication Link. The module resides in a 1771 I/O rack and receives its power from the rack's backplane.

A 1771-KE module must be installed in an I/O chassis. The 1771-KD, 1771-KF, and 1770-KF2 are standalone modules. Modules 1771-KE, 1771-KF, and 1770-KF2 provide either peer-to-peer or master-slave communication between an RS-232-C link, or to a modem link, and the Data Highway.

RS-422-A/Data Highway Interface

A 1770-KF2 provides an interface between an RS-422-A communication link and a Data Highway communication link. The 1770-KF2 is functionally identical to the 1771-KF except that it is a desktop module, provides its own power supply, and supports both RS-232-C and RS-422-A communication.

RS-232-C/RS-422-A Ð PCL Interface

A 1770-KF2 provides an interface between an RS-232-C or RS-422-A asynchronous link and a Peer Communication Link network.

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Software Layers	Each of the physical links just described requires three layers of software
	to enable communication to take place. The layers are defined as follows:
	Application Layer Ð Controls and executes the actual tasks, or
	commands, specified in the communication between stations. To
	program this layer, use the commands described in Chapter 5.
	Network Management Layer Ð Handles queueing, sequencing,
	routing, and error status reporting for communication. If your physical
	link contains only Allen-Bradley PCs, you do not have to program this
	layer. Otherwise, refer to Chapter 5 for a description of how to
	program this layer for an asynchronous link to a computer.
	Data Link Layer Ð Controls the flow of communication over the
	physical link by establishing, maintaining, and releasing the
	communication channel between stations. If your physical link
	contains only Allen-Bradley PCs, you do not have to program this
	layer. Otherwise, refer to Chapter 4 for a description of how to
	program this layer for an asynchronous link to a computer.
	Application Layer
	The application layer concerns the specific commands that you can
	program at a given station to cause that station to communicate over the
	link. This layer is the same for both asynchronous and network links.
	The types of commands that a station can transmit and receive vary with
	the type of processor at that station. Chapter 5 describes the commands
	that each type of PC processor can transmit or receive. To program your
	computer to communicate with a PC, use the appropriate command
	message format shown in Chapter 5.
	Message Structures
	All messages on a network have the same fundamental structure,
	regardless of their function or destination. If you could freeze a block
	while it is in transmission, you would see two types of message bytes:
	Protocol Bytes
	Data Bytes
	Protocol bytes are used by the network to get the message to its
	destination. Data bytes are delivered to the application at the destination.
	The methods by which these bytes are filled is determined by the nature
	of the station from which the transmission block originates. For example,
	if a transaction originates from a PC station, the station interface module

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automatically fills the protocol bytes. If the transaction originates from a computer station, your computer software must supply the necessary protocol. In both cases, the data bytes contain information supplied by application programs.

Command/Reply Cycle

Any network transaction consists of two messages: a command and a reply.

The two parts provide extra data integrity by ensuring that a required action always returns some sort of status, whether an error code or data. As a frame of reference, the command initiator is always referred to as a local station, and a reply initiator is always referred to as a remote station. Unless noted otherwise, whether in a network link or an asynchronous link, our reference will be limited to a single local station and a single remote station.

The network layer protocol distinguishes a command from a reply. Obviously, the data area of a command and its corresponding reply depend on the type of command.

Priority

Each message on a Data Highway link is classified as either high priority or normal priority.

Each message on a PCL is classified as normal priority.

Priority levels of messages determine the order in which stations are polled and allowed to transmit messages. In the polling process, stations with high priority messages will always be given priority over stations with normal priority messages.

You specify the priority level for each command in the message command code. The station that receives a command message must establish the same priority level for its corresponding reply message.

Important: Stations with high priority messages are given priority over stations with normal priority messages throughout the command/reply message cycle. For this reason, a command should be given a high priority designation only when special handling of specific data is

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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 Structures

There are four basis types of command on a Data Highway network or a standalone link:

Read

Write

Diagnostic

Mode Select

Reads

There are two types of read:

Physical

Unprotected

A physical read allows you to read any area of PC memory at a remote station. However, a PC processor cannot originate a physical read command; only a computer can originate a physical read.

An unprotected read can access only the data table area of PC memory.

Both computers and PCs can initiate unprotected reads.

Any read can request up to 122 16-bit words of contiguous data from PC memory.

Writes

We can classify write commands both by their application and by their level of memory access.

As an application issue, writes are divided between bit writes and word writes. Bit writes allow the local station to control bits in the data table of a remote station.

Word writes allow the local station to write up to 121 contiguous words of data into the remote station's memory, provided you abide by the restrictions on memory access discussed next.

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As with reads, writes also are classified by the level of access to PC memory. Non-physical writes can access only the data table at a remote PC; physical writes can access all of user memory, including PC program memory.

Non-physical writes can be further subdivided into protected and unprotected. Protected writes can access only specified areas of the remote PC's data table memory. The accessible areas are defined by memory protection rungs in the remote PC's ladder diagram program. Unprotected writes, on the other hand, can access any area of the remote PC's data table.

In most cases, switch settings on the remote station's interface module can disable the module from executing each of these types of write commands.

Diagnostics

Diagnostic commands have to originate from a device other than a PC. You can use these commands to return status information from a remote or local station or to alter some on-board parameters at a station interface module. Diagnostic commands are particularly useful during a start-up or during on-line debugging.

Mode Select

Mode select commands allow you to load a new PC program from a remote computer station. The operation of these commands varies by PC processor type. These commands can be issued only by a computer.

Network Management Layer

The network management layer is concerned with the specifics of conveying a message safely from its source to its destination. This layer is the same for both asynchronous and network links.

If your physical link contains only Allen-Bradley PCs, you do not have to program anything for this layer; the communication interface modules automatically take care of it. If your physical link contains a computer, then refer to Chapter 5 for a description of how to program this layer at the computer station.

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Generally, you need not be concerned with the interaction of station interface modules on the network.

This means that your application programs at the PCs and computers along the network need not involve themselves with interstation protocol, handshaking, or control of the network link. This is all carried out automatically by the station interface modules. However, an understanding of station interaction is useful both to computer programmers and PC programmers. It allows optimum use of network commands and fault diagnostics.

Error Checking

Error codes can be generated at two places: remote station modules and local station interface modules. For codes that are returned from a local station module, two types of condition can exist:

Application programs use the wrong message format or issue illegal commands.

The local station cannot complete a transaction due to network problems.

A remote station can return only the codes associated with an application problem at the remote station. Typically, these involve either the PC processor being off-line (in Program mode, for example) or the command trying to access memory areas blocked by either the interface module or the user application program.

In the network layer protocol, command message status is returned in a reply status byte. A value of zero in the status byte indicates successful transmission of the corresponding command. It is up to the local application program to display and act on the value of the returned byte.

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Installation

General	This chapter explains how to install the 1770-KF2 module. There are four
	parts to installation:
	Setting Communication Option Switches
	Situating the Module for Operation
	Connecting the Module to the Network and Asynchronous Links
	Observing the Diagnostic Indicators
	Please read the first three chapters of this manual carefully before
	attempting any of the installation steps.

Communication Option Switches The KF2 module has 8 switch assemblies (Figure 3.1) that enable you to select various communication options. The switch assemblies and their corresponding options are:

Switch Assembly	Communication Option
SW-1	Asynchronous Link Features
SW-2, SW-3, SW-4	Station Number
SW-5	Network Link Communication Rate
SW-6	Asynchronous Link Communication Rate and Diagnostic
	Commands
SW-7	Selecting the Network Link
SW-8	RS-232-C/RS-422-A Selection

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Figure 3.1

Communication Option Switches

				Network Link
				Communication
	Asynchronous Link			Rate (SW-5)
						Asynchronous Link
	Features (SW-1)
						Communication
			Station Number			Rate (SW-6)
RS-232-C/RS-422-A			(SW-2, SW-3, SW-4)				Network Link
							Selection
Selection (SW-8)
							(SW-7)
O 1 2	O 1 2 3 4 5	O 1 2 O 1 2 3		O 1 2 3	O 1 2	O	1 2 3 4	O 1 2
N	N	N	N	N	N	N		N
O	O	O	O	O	O	O		O
F	F	F	F	F	F	F		F
F	F	F	F	F	F	F		F
		Front View		Side
		O 1	2	ON ON ON
		N
		O		OFF	OFF		OFF
		F						13529
		F

Important: The KF2 reads the status of the communication option switches only at power-up, so you must make your selection with the KF2's power off.

Asynchronous Link Features

The following table shows you how to set the asynchronous link features using Switch Numbers 1, 2, and 5.

	If You Want			With
	to Select	With Error	With	Embedded			SW-1
	Protocol as:	Check as:	Parity as:	Responses:
					1	2	3		4	5
	Full Duplex	BCC	None	No	OFF	OFF	N/A		N/A	OFF
	Full Duplex	BCC	Even	No	ON	OFF				OFF
	Full Duplex	BCC	None	Yes	OFF	ON				OFF
	Full Duplex	BCC	Even	Yes	ON	ON				OFF
	Half Duplex	BCC	None	No	OFF	OFF				ON
	Half Duplex	BCC	Even	No	ON	OFF				ON
	Full Duplex	CRC	None	Yes	OFF	ON				ON
	Half Duplex	CRC	None	No	ON	ON				ON

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Switch 3 determines whether the asynchronous port of the KF2 module can detect duplicate messages transmitted to it.

	If You Want Your Module to:	Set Switch 3:
	Detect and Ignore Duplicate Messages	ON
	Accept All Messages Regardless of Duplication	OFF

Switch 4 determines whether the module uses and recognizes the following handshaking signals: data set ready, request to send, clear to send, data carrier detect, and data terminal ready.

	If You Want the Module's Asynchronous Port to:	Set Switch 4:
	Use Handshaking Signals	ON
	Ignore Handshaking Signals	OFF

Important: If you select half-duplex, the KF2 uses handshaking signals even if Switch 4 is set OFF.

Station Number

Switch Assemblies SW-2, SW-3, and SW-4 are for setting the network station number of the KF2 module. For the Data Highway, the station number is a 3-digit octal number that identifies the KF2 module as a unique station. Valid station numbers for the KF2 module in Data Highway mode are 010 to 077 and 110 to 376 octal. For a PCL, the station number is 2 digits; set both switches in SW-2 OFF. Valid station numbers for the KF2 in PCL mode are 00 to 77 octal.

Figure 3.2 shows an example of how to set the KF2 station number to 037 octal. The switches in Assembly SW-2 set the first (left-most) digit of the station number; Switch Assembly SW-3 sets the middle digit; and Switch Assembly SW-4 sets the last (right-most) digit.

Station numbers play an important part in the polling scheme described in Chapter 2. They can also influence the order in which mastership is transferred between network stations. Therefore, we recommend that you always begin numbering stations with the lowest possible number and continue with the next available number in sequence.

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Figure 3.2

Station Number

Switch Groups

SW-2	SW-3	SW-4	ON	ON
O 1 2	O 1 2 3	O 1 2	OFF
			3
N	N	N
O	O	O	ON
F	F	F
F	F	F	OFF	OFF

First Digit

If You Want	Set Switches
to Set This
Digit:	No. 1	No. 2
0	OFF	OFF
1	OFF	ON
2	ON	OFF
3	ON	ON

Second and Third Digits

If You Want		Set Switches
to Set This
Digit:	No. 1		No. 2	No. 3
0	OFF		OFF	OFF
1	OFF		OFF	ON
2	OFF		ON	OFF
3	OFF		ON	ON
4	ON		OFF	OFF
5	ON		OFF	ON
6	ON		ON	OFF
7	ON		ON	ON

Switch Setting Example: Station No. 037

Switch Group	SW-2				SW-3			SW-4
Station No. Digits		0			3			7
Switch No.	1		2	1	2	3	1	2	3
Switch Setting	OFF		OFF	OFF	ON	ON	ON	ON	ON

13531

Network Communication Rate

Switch Assembly SW-5 lets you select the communication rate for the KF2 module's network link.

Important: Set both switches ON for a network communication rate of 57,600 bits per second. Be sure to set all modules on the network link for this communication rate.

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Figure 3.3

Switch Settings for Network Link

SW±5

O 1 2

N

Both switches ON for

O 57,600 bits per second

F

F

13514

Asynchronous Communication Rate and Diagnostic Commands

Switch Assembly SW-6 lets you select the communication rate and diagnostic commands for the KF2 module's asynchronous port.

Communication Rate

Set the communication rate switches as shown:

Bits per		Set Switch:
Second as:
	1		2			3
110	OFF		OFF			OFF
	ON		OFF			OFF
300
600	OFF		ON			OFF
1,200	ON		ON			OFF
2,400	OFF		OFF			ON
4,800	ON		OFF			ON
9,600	OFF		ON			ON

Diagnostic Commands

Switch 4 determines how the KF2 module treats diagnostic commands sent to it by a remote Data Highway station. You can connect the asynchronous port of the KF2 module directly to a 1771-KG, 1773-KA, or 1775-KA communication interface module (Figure 1.2). In such applications, you can set Switch 4 so that the KF2 module either executes any received diagnostic commands itself or passes those commands to the other attached communication module.

	If You Want Your Module to:	Set Switch 4:
	Execute Received Diagnostic Commands	ON
	Pass Any Received Diagnostic Commands to the	OFF
	Attached Asynchronous Device

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Switch 4 relates only to diagnostic commands sent to the KF2 module from a remote Data Highway station. Since only computers can transmit diagnostic commands, the remote station must be a computer connected to the Data Highway by means of another KF2 module. At the computer station, the setting of Switch 4 does not affect any diagnostic commands that the computer sends to its local KF2 module. The local module always retransmits the command message over the Data Highway without executing it. Figure 3.4 illustrates these concepts.

Figure 3.4

Effect of Switch 4 on Diagnostic Commands

		Switch 4 ON
		1770-KF2 Module
Computer	1770-KF2 Module
	Data	1771-KG Module
	Highway
	Link	PLC-2/15 Processor
	To Other Stations
Diagnostic Command Path
Reply Message Path
		Switch 4 OFF
		1770-KF2 Module
Computer	1770-KF2 Module
	Data	1771-KG Module
	Highway
	Link	PLC-2/15 Processor
	To Other Stations

11691

You can have more than one computer station on a network, and one computer can transmit diagnostic commands to the others. At the receiving computer station, if Switch 4 is OFF, the local KF2 module will pass the diagnostic commands to the computer. In such cases, you will have to write computer application programs to handle those commands at the receiving station. If Switch 4 is ON at the receiving station, the local KF2 module itself will execute the incoming diagnostic commands.

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