Rockwell Automation 1771-DA,D17716.5.13 U MNL 1771-DA ASCII I/O MODULE - Manual (Page 180)

ASCII Module
PLC-2 Family Processors
Appendix A
AĆ12
Figure A.5
Local System Example
1771-AL
1771-DA
Rack No. 1
1771-AL
1771-DA
Rack No. 2
1771-AL
1771-DA
Rack No. 3
1771-AL
1771-DA
Rack No. 4
11841
PLC-2/30
Solution:
The facts of the problem are:
Program length = 4K words
Number of chassis = 4 rack numbers
Number of block transfer words, W = 64 (read) or 2 (write)
1. Calculate the system values.
Processor Scan Time, PS = (5ms/1K words) x (4K words) = 20ms
Processor I/O Scan Time, PIO = (0.5ms/rack number) x(4 rack
numbers) = 2ms
Number of Words Transferred, W = 64(read) or 2 (write)