Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM User Manual
Page 397
Publication AG-UM008C-EN-P - February 2005
Sample Ladder Logic E-15
The next three rungs create a data file comparison routine. This rung clears the index register (S:24) to prepare it for use in the Not Equal comparison instruction.
0003
CLR
Clear
Dest
S2:24
0<
CLR
Index Register
If any values differ between the first three words of B3:0 and N7:0, copy B3:0-7 into N7:0-7, trigger the MSG (which will write N7:0-7 to the Master) and jump out of the routine.
0004
LBL
Q2:1
Compare
Rung
NEQ
Not Equal
Source A
#B3:0
0000000000000000<
Source B
#N7:0
0<
NEQ
Data Compare Buffer
COP
Copy File
Source
#B3:0
Dest
#N7:0
Length
8
COP
MSG Write Buffer
U
N7:90
15
MSG
Enable
JMP
Q2:2
Jump to
MSG Rung
If the current value comparison found no differences, increment the index register. As long as the index register (S:24) is still less than the number of words being compared, jump back to the previous rung to
perform the next value comparison. Otherwise, fall out of the routine.
0005
ADD
Add
Source A
S2:24
0<
Source B
1
1<
Dest
S2:24
0<
ADD
Index Register
LES
Less Than (A
S2:24
0<
Source B
3
3<
LES
Index Register
JMP
Q2:1
Jump to
Compare
Rung
The next two rungs are the MSG rungs. Timer T4:1 is used as the MSG timeout timer, with a preset value of 10 seconds. Note that the MSG timeout value should be set to at least twice the channel 0 poll timeout
value.
0006
LBL
Q2:2
MSG Rung
N7:90
15
MSG
Enable
N7:90
13
MSG
Done
N7:90
12
MSG
Error
EN
DN
TON
Timer On Delay
Timer
T4:1
Time Base
1.0
Preset
10<
Accum
0<
TON
MSG Timeout Timer
T4:1
DN
MSG
Timer
L
N7:90
8
MSG
Timeout
"Report-by-exception" write instruction to the SLC Master. This MSG block is configured to write 8 elements ( words) from this Slave's Source File N7:0, out channel 0, to the Master's (Target Node Address 0)
Target Destination File N7:10. MSG can only be triggered if DF1 is the active protocol.
0007
S2:0
11
Active
Protocol
EN
DN
ER
MSG
Read/Write Message
Read/Write
Write
Target Device
500CPU
Control Block
N7:90
Control Block Length
7
Setup Screen
MSG
Write MSG to Master
0008
END