Watlow CLS200, MLS300 and CAS200 User Manual download pdf (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).

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Watlow CLS200, MLS300 and CAS200 User Manual Page 14

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