Rockwell Automation 1771-QC , D17716.5.25 SER/B SERVO POS - Manual (Page 174)

Chapter 8
8Ć13
For example, consider a Mini-PLC-2/15 controller with one 1771-M3
controller in its I/O chassis. There are no other block transfer modules,
and program length is 2K words.
To calculate worst case time between write block transfers for this system
follow these steps:
1. Write down known values:
program length = 2K words
block length = 64 (write) or 10 (read)
2. Calculate processor scan time:
PS = (24ms/K word)(2K words) = 48ms
3. Calculate block transfer times:
TW = 0.1ms + [(0.16ms/word)(64 words)] = 10.34ms
TR = 0.1ms + [(0.16ms/word)(10 words)] = 1.7ms
4. Calculate time between write transfers:
TBT = 2(PS) + TR + TW = 96 + 10.34 + 1.7 = 108.04ms
Figure 8.5 shows the formats of block transfer instructions for a PLC-3
processor. For each block transfer instruction you must specify:
I/O rack
I/O module group within the I/O rack
I/O module slot within the I/O module group
PLCĆ3 Block Transfer
Instructions