Watlow CLS200, MLS300 and CAS200 - Manual (Page 13)

Chapter 1: ANAFAZE/AB Protocol
Communications Specification 7
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
with the 7th bit set—in other words, it sends an x41 or x48.
STS (The Status Byte)
• The controller uses the status byte, or STS, to return general status
and error flags to the host software. (The controller ignores the status
byte in the host software's command packet.) The next table shows
status byte values and definitions.
• An “x” in the status bytes below indicates that the associated nibble
may contain additional information. In most cases, the status byte is
composed of two independent nibbles. Each nibble is independent
so that two codes can return at once. For example, status code F1
indicates that data has changed (Fx) and the controller is being
updated through the front panel (x1).
TNSL
• Least significant byte of the transaction number. This is the first half
of a “message stamp.”
• The controller sends back the TNSL and TNSH exactly as it received
them, so host software can use the TNSL and TNSH bytes to keep
track of message packets.
TNSH
• Most significant byte of the transaction number. This is the second
half of the “message stamp.”
Status
in Hex
Description
00 The controller has nothing to report, or AB protocol is selected.
01 Access denied for editing. The controller is being updated through the
front panel.
02 AIM Comm failure.
A0 A controller reset occurred.
Cx The controller received a command that was not a block read or block
write. (Command Error)
Dx The block write command attempted to write beyond a particular parame-
ter block boundary, or the host software attempted to access a data table
block that does not exist. (Data Boundary Error)
Ex The Alarm_Status variable has changed. The software should query the
alarm status block to determine the particular alarm flag that changed.
Fx The controller altered shared data, either internally (from the firmware) or
externally (from the keyboard). The host software should read the Data
Changed Register to determine which data has been altered and update
its own run-time memory.