Rockwell Automation RECOMM-IBUS Interbus Communications Module - Manual (Page 70)

7-10 Interbus Communications Module
7.3.3 PCP Write Message Format
PCP Writes require the following Command and Reply message
formats:
Command
Reply
Table 7.8 – Command Message Format for PCP Writes
Word Name Description
0 CR The Communication Reference (CR #) to
write to
1 Index The index of the variable to write
2 Sub Index The sub-index of the variable to write (not
used)
3 Data
Length The # of bytes of data following (1, 2, or 4
bytes)
4 Data
Word 1 Contains 8-bit (1 byte) write data (stored in
the high byte), 16-bit, (2 byte) write data,
and the most significant word for 32-bit (4
byte) write data
5 Data
Word 2 Least significant word for 32-bit (4 byte)
write data
Table 7.9 – Reply Message Format for PCP Writes
Word Name Description
0 Command
Word Echo Echo of the Command Word (0008h)
1 Message
Length Number of words following
2 CR The Communication Reference (CR #) the
Reply is from
3 Result Result Code:
0=Success
FFFFh = Timeout
FFFEh = Out of buffers to store the reply
FFFDh = Invalid CR
FFFCh = Could not connect to device with
CR
FFFBh = Reply of Command bigger than
buffer