Watlow CLS200, MLS300 and CAS200 - Manual (Page 14)

8 Communications Specification
Chapter 1: ANAFAZE/AB Protocol
ADDL
• The low byte of the beginning data table address of the block of data
to read or write.
ADDH
• The high byte of the beginning data table address of the block of data
to read or write.
DATA
• The new values to be set with a write command, or the requested data
in a response to a read command.
DLE ETX
• Every packet of information must end with the codes DLE ETX.
These codes signal the end of a transmission.
BCC or CRC
• Communications packets include a one- or two-byte error check at
the end of the packet. There are two error check methods: Block
Check Character (BCC), which requires 1 byte, and Cyclic Redun-
dancy Check (CRC), which requires 2 bytes.
Error Checking
Watlow Anafaze recommends that you use the default error check
method, BCC. It is easier to implement than CRC, and it is acceptable
for most applications.
Select one error check method and configure both software and
controller for that method, or they will be unable to communicate.
The error check methods work this way:
Block Check Character (BCC)
BCC checks the accuracy of each message packet transmission. It
provides a medium level of security. The BCC is the 2’s complement of
the 8-bit sum (modulo-256 arithmetic sum) of the data bytes between
the DLE STX and the DLE ETX. (1’s complement +1)
• BCC does not detect transposed bytes in a packet.
• BCC cannot detect inserted or deleted 0 values in a packet.
• If you have sent an x10 as data (by sending DLE x10) only one of the
DLE data bytes is included in the BCC’s sum (the DLE = x10 also).