Plc programming considerations appendix a – Rockwell Automation 2711 PANELBUILDER SOFTWARE USER MANUAL User Manual
Page 368
PLC Programming Considerations
Appendix A
A-4
Figure A.1
BiĆDirectional Block Transfer Example (PLCĆ5/15)
BTR
BLOCK TRANSFER READ
Rack:
3
Group:
2
Module:
0
Control Block:
N10:0
Data File:
N11:0
Length:
32
Continuous:
N
Write
Enable
N10:5
/
Read
Enable
N10:0
/
15
15
(EN)
(DN)
(ER)
Write
Enable
N10:5
/
Read
Enable
N10:0
/
15
15
(EN)
(DN)
(ER)
20237
Read
Done
N10:0
13
(EN)
(DN)
(ER)
BTW
BLOCK TRANSFER WRITE
Rack:
3
Group:
2
Module:
0
Control Block:
N10:5
Data File:
N12:0
Length:
32
Continuous:
N
FAL
FILE ARITHMETIC/LOGICAL
Control:
R6:5
Length:
32
Position: 0
Mode: ALL
Dest: #N13:0
Expression:
#N11:0
Move Read File to Verified" Read File
Your PLC program should use the data in the “verified” read file. Because
read data is presented asynchronously to the program scan, data could
change during the program scan. Putting the above rungs at the beginning
of the program can assure that all ladder logic sees the same data in the
same program scan.