Rockwell Automation 20-COMM-I Interbus Adapter - Manual (Page 80)

6-18 Using Explicit Messaging (PCP Communications)
Figure 6.3 LAD5 - PCP Read Subroutine (Continued)
If the PCP Read Reply message indicates that the result was "not good" (N22:24 <> 0), then zero out the data area of the Reply
message (might contain leftover data from a previous successful PCP Read).
0010
M1:1.0
15
Status
Message
Present
B3:47
2
PCP Read
Reply Msg
1-Shot
NEQ
Not Equal
Source A
N22:24
0<
Source B
0
0<
PCP Read
Reply Msg
Result
MOV
Move
Source
0
0<
Dest
N22:26
325<
MOV
PCP Read
Reply Msg
Data Word #1
MOV
Move
Source
0
0<
Dest
N22:27
0<
MOV
PCP Read
Reply Msg
Data Word #2
The PCP Read Reply 1-shot is used so the subroutine processes the Reply message only once.
0011
M1:1.0
15
Status
Message
Present
L
B3:47
2
PCP Read
Reply Msg
1-Shot
When the Command / Status Message handshake is complete, reset the 1-shot bits and exit the PCP Read routine by turning the
"Execute PCP Read" bit off (B3:47/0)
0012
M0:1.0
15
Command
Message
Acknowledge
M1:1.0
15
Status
Message
Present
U
B3:47
0
Execute
PCP Read
Subroutine
U
B3:47
1
PCP Read
Routine
1-shot
U
B3:47
2
PCP Read
Reply Msg
1-Shot
U
M0:1.0
15
Command
Message
Acknowledge
0013 END
20COMM-UM007A-EN-P.book Page 18 Tuesday, January 22, 2002 10:52 AM