Rockwell Automation 2711 PANELBUILDER SOFTWARE USER MANUAL - Manual (Page 379)

PLC Programming Considerations
Appendix A
A-15
Ladder Program for Remote I/O
Remote I/O addresses correspond to the addresses in the block transfer
read and write files, with inputs to the read file and outputs to the write
file. For example, you would monitor an input in rack 1, module group 3,
bit 5, and energize an output in rack 2, module group 4 bit 12, as follows,
based on example block transfer files (Figure A.8) at 300 (read) and 200
(write).
Figure A.10
Ladder Program for Remote I/O
313
] [
05
20220
224
( )
12
Although system response times are quite predictable, they are very
application dependent. Methods for determining response times differ,
depending on the type of PLC processor and the PLC system
configuration.
Discrete Data Response Time
The following formula can generally be used to determine the worst case
time (in ms) required to transfer data to or from the terminal. This includes
the terminal’s input or display processing time:
Program Scan Time + I/O Scan time + Terminal Process Time
Program Scan Time
This determines how quickly the PLC program can update or act on the
discrete data. Subroutine and/or “immediate I/O” instructions are
sometimes used to reduce the effective program scan time when necessary.
The program scan depends on the type of PLC processor and PLC program
size. Refer to your programmable controller user’s manual. Some typical
program scan times include the following:
System Response Times