
PLC Programming Considerations
Appendix A
A-19
Table A.C
Transfer
T
imes for PLC5/10/12/15/25 at 57.6K Baud
Transfer Local Chassis Remote Chassis
Read 0.9 + 0.1 W ms 9 + 21.3 C + 0.3 W ms
Write 0.9 + 0.1 W ms 13 + 30 C + 0.3 W ms
Table A.D
Transfer
T
imes for PLC5/40/60 at 57.6K Baud
Transfer Local Chassis Remote Chassis
Read 0.9 + 0.1 W ms 4 + 8 C + 0.3 W ms
Write 0.9 + 0.1 W ms 4 + 8 C + 0.3 W ms
C = number of remote I/O chassis
W = number of transfer words
Some typical transfer times with no requests in the queue are as follows:
Table A.E
Typical
T
ransfer T
imes
Transfer Number of Words Local Chassis Remote /w 3 Chassis
on Channel
Read 10 1.9 ms 54 ms
Write 10 1.9 ms 79 ms
Read 32 4.1 ms 61 ms
Write 32 4.1 ms 86 ms
Terminal Process Time
Terminal process time is less than 2.0 ms (typical) per dynamic object on
the screen being displayed.
Program Scan Time
The block transfer timing formula does not include the PLC program scan
time (PS). The PLC-5 processor can execute block transfer instructions
asynchronously to the program scan, reducing the affect of the program
scan time. However, your program scan time will affect how quickly the
PLC data can be updated or acted on by other parts of the PLC program.
This can be calculated by adding the program scan time to the
formula (IE + WQ + TT + TP ). Sub-routines or “immediate I/O”
instructions can be used to reduce the effective program scan time.
Kommentare zu diesen Handbüchern