Rockwell Automation 20-COMM-I Interbus Adapter - Manual (Page 66)

6-4 Using Explicit Messaging (PCP Communications)
Figure 6.2 Memory Map
The ladder example used in this manual uses Input (I:) and
Output (O:) files for I/O messaging (Logic Command/Status, Reference/
Feedback, and Datalinks) and M Files for PCP
messaging (See
Chapter 4 , RSLogix 500 SST Interbus Scanner
Configuration .)
The first word in the Command Interface memory area is the Command
(M0) or Status (M1) word. The remaining words form a buffer to pass
command data to and from the scanner. The M0 file contains the buffer
for the command written by the SLC and the M1 file contains the reply
to the SLC written by the scanner.
The lower six bits in the Command word are command bits to the
scanner. Commands are initiated by setting bits in this Command word.
The scanner acknowledges the command by setting bits in the Status
word. The high bit is either the Message Acknowledge bit (command
word) or the Message Present bit (Status word).
Table 6.1
Bit Description
0 PCP Start
1 PCP Stop
2 PCP Read
3 PCP Write
4 PCP Command
5 IBS Command
15 Message acknowledge (Command) / Message present (Status)
O/I
M0/M1
O/I:0
M0/M1:(G:5-1)
M0/M1:(G:5)
M0/M1:(G:5+1)
M0/M1: (G:5+G:6-1)
Process Data
(I/O Messaging)
Command/Status word
Command/Response Buffer
(Explicit Messaging)
M0/M1:0
20COMM-UM007A-EN-P.book Page 4 Tuesday, January 22, 2002 10:52 AM