WATLOWCLS200, MLS300, and CAS200 Communications Specification

This reference guide is designed to help applications software

programmers with the following tasks:

• Interface to Watlow Anafaze MLS300, CLS200, MLS and CLS controllers, and the CAS200 and CAS scanners via serial communications.

• Modify the communications Anafaze protocol driver in the Watlow 

Anafaze Communications Driver Kit. (If you have the communications driver kit, you don’t need to read this manual unless you want 

to modify the communications driver.)

In This Manual

The following sections are included in this guide: 

Chapter 1: Anafaze/AB Protocol. Gives an overview and explanation

of the Anafaze/Allen Bradley communications protocol.

Chapter 2: Modbus-RTU Protocol. Gives an overview and

explanation of the Modbus-RTU communications protocol

Chapters 1 and 2: Data Table Summary. Provides standard controller

data table maps for the parameters (one for each protocol).

Chapter 3: Parameters Description. Describes each parameter.

Appendix A: Communications driver.

Glossary: Explanation of commonly used terms and acronyms.

NOTE

This reference guide is not a tutorial. It does not explain

how to use the controller; it is not a programming reference; it also does not explain PID control, alarms, linear

scaling, or other topics that are explained in detail in the

controller manuals. If you need additional information

about a topic covered in this reference guide, consult the

documentation included with your controller.

Chapter 1: ANAFAZE/AB Protocol

This section explains the ANAFAZE/Allen Bradley protocol used in

Watlow Anafaze MLS, CLS, and CAS devices. These controllers

operate on serial communications links (EIA/TIA-232 or EIA-TIA-485)

at either 2400 or 9600 baud. They use 8 data bits, one or 2 stop bits, and

no parity.

Protocol Syntax

The controllers use a half-duplex (master-slave) protocol to interface to

high-level software. The host software is considered the “master” and

the controller is considered the “slave.” In other words, the software can

request information from the controller or download information to the

controller. The controller can only respond to communications

transactions initiated by the host software. The controller cannot initiate

communications.

The controller and host software communicate by sending and receiving

information in a “packet” format. A packet consists of a sequence of

bytes in a specific format; it can be as large as 256 bytes of data. (For

more information about packets, see the Packet Format section later in

this chapter.)

The numbers in the packet are sent in binary format. However, our

examples show bytes in hexadecimal format.

Control Codes

Watlow Anafaze abbreviates control codes this way

Chapter 1: ANAFAZE/AB Protocol

Transaction Sequence

Here are the four steps in a transaction between the host software and

the controller. The following example shows the transaction as an

exchange of packets. The example also assumes that there are no

communication errors in the exchange.

(1) The host software sends a packet that contains a read command or 

write command.

(2) The controller sends a DLE ACK to the host software.

(3) The host software receives a reply packet from the controller. 

(4) The host software sends a DLE ACK.

The following flowchart shows a transaction with no error handling.

NOTE

Due to the difference between the processing speeds of the

controller and PCs, it may be necessary to delay the computer's acknowledgement (ACK) in order for the controller

to receive it. A delay of 200 ms should suffice

Packet Format

Messages are transmitted in the form of packets. Command and reply

packets specify the source and destination addresses, whether to read or

write, the block of data to read or write, etc.

A packet contains a sequence of binary bytes formatted this way:

Sending Control Codes

To send a control code, send a DLE before the control code to

distinguish it from data.

Sending a DLE as Data

When you send a byte with an x10, (a DLE), the controller and software

interpret it as a command. Therefore, to send a DLE as data, send

another DLE immediately before it (DLE DLE). 

Codes in a Packet

This section describes the sequence of bytes in a packet, in the order the

host software or controller sends them.

DLE STX

• The DLE STX byte signals the beginning of a transmission. Every 

packet of information starts with the control codes DLE STX. 

DST

• The DST byte is the address of the destination device (usually a controller; the first Watlow Anafaze controller is at x08).

NOTE

When host software communicates with an MLS, a CLS, or

a CAS in ANAFAZE or AB protocol, it does not send the

controller’s actual address. Since the protocol reserves

device addresses 0 to 7, the host software sends the value

(controller address + 7), instead of the actual device

address.

SRC

• The SRC byte is the device address of the packet’s source. The host 

software is usually designated address x00.

DLE STX DLE ETX BCC/CRC

DST SRC CMD STS TNSL TNSH ADDL ADDH DAT

CMD

• The CMD byte indicates the command that the host software sends 

to the controller. The software sends a read (x01) or write (x08). 

When the controller replies, it returns the read or write command