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It is assumed that the program contains 5,000 instructions requiring an average
of 0.156 µs each to execute, and that nothing is connected to the RS-232C port
and no SYSMAC NET/SYSMAC LINK Unit is mounted.
Computer
Slave Rack
Host Link Unit
Remote I/O
Master Unit
CPU Rack
8-point
Input Units
8-point
Output Units
12-point
Output Units
16-point
Input Units
Calculations The equation for the cycle time is as follows:
Cycle time = Overseeing time + Program execution time
+ I/O refreshing time + Host Link Unit servicing time
+ Peripheral device servicing time
Process Calculation With Peripheral
Device
Without
Peripheral Device
Overseeing Fixed 0.7 ms 0.7 ms
Program execution 0.156 µs/instruction
× 5,000 instructions
0.78 ms 0.78 ms
I/O refresh See below. 2.58 ms 2.58 ms
Host Link servicing Fixed 6.0 ms 6.0 ms
Peripheral device
servicing
0.7 + 0.78 + 2.58 +
6 = 10.06
10.06 × 0.05 = 0.50
0.50 ms 0.0 ms
Cycle time Total of above 10.56 ms 10.06 ms
The I/O refreshing time would be as follows for three 8-point Input Units and
three 8-point Output Units mounted in the CPU Rack, and eight Units mounted in
a Slave Rack.
+ 1.1 ms + 8 Units × 0.17 ms = 2.58 ms
8 pts
(8 pts × 3) + (8 pts × 3)
× 20 µs
Calculating Cycle Time Section 6-2