Rockwell Automation 1771-PD PID MODULE (+DU) - Manual (Page 118)

Programming
Chapter 3
3Ć75
A normal load/enter sequence contains seven consecutive alternating read
and write block transfers.
dynamic block (write)
status block (read)
loop 1 block (write)
status block (read)
loop 2 block (write)
status block (read)
dynamic block (write)
Using the value of TW’ = 132msec for a single read or write operation
from step 2, the total time for a normal load/enter sequence is:
T
LE
= (7) x (TW’)
= 7 x 132
= 924msec
Example Problem 2
A Pid module in a remote system controls two expanded loops. The
remote system contains another block transfer module that transfers 64
words.
Processor = PLC-2/30
I/O = 6 remote chassis (six rack numbers)
Program = 8K words
Number of words transferred = 18 (PID)
Number of words transferred = 64 (other module)
a. Calculate the time for a single read or write block transfer.
b. Calculate the time required for a load/enter sequence when the
other block transfer module is performing block transfers.