Watlow CLS200, MLS300 and CAS200 - Manual (Page 10)

4 Communications Specification
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.
( continued on next page )
NOTE
Due to the difference between the processing speeds of the
controller and PCs, it may be necessary to delay the com-
puter's acknowledgement (ACK) in order for the controller
to receive it. A delay of 200 ms should suffice.
ACK Acknowledged
Signals that a syntactically correct packet has been received.
06 06
NAK Not Acknowledged
Signals that an incorrect, invalid packet has been received.
21 15
Code Meaning
Decimal
Value
Hex
Value
Send
command
packet
Receive
DLE ACK Receive valid
reply packet Send
DLE ACK