Rockwell Automation RECOMM-IBUS Interbus Communications Module - Manual (Page 64)

7-4 Interbus Communications Module
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 section 5.5, Configuring the RSLogix 500 SST
Interbus Scanner.)
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).
The ladder example used in this manual performs PCP Reads and
PCP Writes.
Figure 7.2 – Memory Map
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
Table 7.2 – Command Word Bit Descriptions
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)