Watlow CLS200, MLS300 and CAS200 - Manual (Page 9)

Chapter 1: ANAFAZE/AB Protocol
Communications Specification 3
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:
Code Meaning
Decimal
Value
Hex
Value
DLE Escape code
Signals the start of the other control code character sequences.
16 10
STX Start Text
Begins a transmission.
02 02
ETX End Text
Ends a transmission.
03 03
ENQ Request Resend
Tells the controller to resend its last ACK or NAK. Host software
sends this command, and the controller responds to it.
05 05