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Chapter 2 Specification of Communication port for CPU module

2 – 26

[Calculation method of communication processing time]

Communication processing time can calculate using the following methods, and is calculated on the basis of the

transmission interval of ASR.

(Example)

- Whole processing time (ASR transmission interval) … 40ms = 40,000µs

- System program processing time (1ms cyclic processing) … 160µs

- Scan time (Displayed value of CPU status current value) (*) … 2ms = 2,000µs

- END processing time (Fixed) (*) … 80µs

- I/O refresh processing time (In mounting 66 module with 16-point I/O) (*) … 66µs

- System processing time (Setting by Control Editor) … 1ms = 1,000µs

(*) Operation time for one scan

(a) System program processing time:

160 [µs/time] × 40 [time] (Execution times in 40ms) = 6,400[µs]

(b) Number of scan times of user program:

(Whole processing time - (a)) / (Scan time + END processing time + I/O refresh time + System processing time)

= ( 40,000[µs] - 6,400[µs] ) / ( 2,000[µs] + 80[µs] + 66[µs] + 1,000[µs] )

≅ 10.7 [time]

2,000 [µs/time] × (b) = 2,000 [µs/time] ×10.7 [time] = 21,400 [µs]

(d) System processing time:

1,000 [µs/time] × (b) = 1,000 [µs/time] ×10.7 [time] = 10,700 [µs]

Communication processing time = (c) + (d) = 21,400 [µs] + 10,700 [µs] = 32,100 [µs] = 32.1ms

In this example, the communication processing time is 32.1ms. If processing of task code communication and ASR

communication is 32.1ms or less, delay of communication response does not occur.

System

program

processing

time

6.4 [ms]

(a)

Communication processing (Task code communication and ASR

communication)

Scan time + System processing time

32.1 [ms]

END processing time: 80[µs] ×10.7[time] ≅ 0.9[ms]

I/O refresh processing time: 66[µs] ×10.7[time] ≅ 0.7[ms]

Whole processing time 40ms

Figure 2.25 Calculation of communication processing time

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