Rockwell Automation 1771-QA Stepper Positioning Assembly User Manual - Manual (Page 61)

3–39 Programming and Operation
Publication 1771-UM002A–EN–P – May 2000
Example Problem 1
A PLC-2/30 programmable controller is controlling 4 I/O racks in
remote configuration (Figure 3.18). A 3-axis stepper positioning
assembly is located in each rack. Assume that the stepper controller
module is operating in default mode and that the ladder diagram
program contains 4K words (K 1024). There are no other block
transfer modules in the system.
Figure 3.18
Remote System Example
PLC–2/30
1772–SD
1771–AS
1771–QA
Rack No. 1
1771–AS
1771–QA
Rack No. 2
1771–AS
1771–QA
Rack No. 3
1771–AS
1771–QA
Rack No. 4
10535
10,000’ System
What is the worst case time between two consecutive write block
transfers for this system when a 64 word moveset block is
transferred to the stepper positioning assemblies and a ten word
status block is returned to the PC processor?
Solution
1. Write down the known facts.
Program length = 4K words
Number of chassis = 4 rack numbers
Number of default block transfer words = 64 words (write),
10 words (read)
2. Calculate the system values.