Rockwell Automation 20-COMM-I Interbus Adapter - Manual (Page 79)

Using Explicit Messaging (PCP Communications) 6-17
Figure 6.3 LAD5 - PCP Read Subroutine (Continued)
Copy the PCP Read Command message to the scanner for transmission on the network.
0004
B3:47
1
PCP Read
Routine
1-shot
COP
Copy File
Source
#N22:10
Dest #M0:1.0
Length 4
COP
The PCP Read Command 1-shot is used so the subroutine processes and sends the Command only once when called by the
MAIN PGM
0005 L
B3:47
1
PCP Read
Routine
1-shot
When the scanner acknowledges the PCP Read command, turn the Command word PCP Read bit OFF (originally comes from
N22:10 which was COPied to M0: above).
0006
M1:1.0
2
Status
PCP Read
U
M0:1.0
2
Command
PCP Read
When the scanner Status word indicates that a message is available, copy the message for processing and handshake with the
scanner by turning the Command word Message Acknowledge bit ON.
0007
M1:1.0
15
Status
Message
Present
B3:47
2
PCP Read
Reply Msg
1-Shot
COP
Copy File
Source
#M1:1.0
Dest #N22:20
Length 8
COP
PCP Read
Reply Msg
Status Word
L
M0:1.0
15
Command
Message
Acknowledge
If the Reply contains only 1 byte of data, then the high and low bytes need to be swapped (e.g. a value of "5" will be stored as a
"0005" as opposed to "0500".
0008
M1:1.0
15
Status
Message
Present
B3:47
2
PCP Read
Reply Msg
1-Shot
EQU
Equal
Source A
N22:25
2<
Source B
1
1<
EQU
PCP Read
Reply Msg
# Bytes of Data
SWP
Swap
Source
#N22:26
Length 1
SWP
PCP Read
Reply Msg
Data Word #1
If the Reply does not contain 4 bytes of data, then the parameter is not 32-bit and Data Word #2 needs to be zero'd (might
contain leftover data from a previous 4-byte PCP Read).
0009
M1:1.0
15
Status
Message
Present
B3:47
2
PCP Read
Reply Msg
1-Shot
NEQ
Not Equal
Source A
N22:25
2<
Source B
4
4<
PCP Read
Reply Msg
# Bytes of Data
MOV
Move
Source
0
0<
Dest
N22:27
0<
MOV
PCP Read
Reply Msg
Data Word #2
20COMM-UM007A-EN-P.book Page 17 Tuesday, January 22, 2002 10:52 AM