Omron CVM1-CLK21, Operation Manual

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202
Data Link I/O Response Time Section 8-3
1,2,3... 1. The input arrives in the PC just after I/O refreshing, causing a delay of up
to one cycle before the input is read into the PC.
2. Data exchange occurs just after the PC at node #1 passes the token that
makes it the polling node, causing a delay of up to one communications cy-
cle time before the data is transferred in data link processing.
3. The data transferred in data link processing arrives at the PC at node #7
after data exchange, so the data will not be read into the PC until the next
data exchange, causing a delay of up to one cycle.
The maximum number of words that can be exchanged in a single data ex-
change is approx. 7,800 words for CS/CJ-series PCs, approx. 3,700 words
for CVM1 and CV-series PCs, approx. 4,000 for C200HX/HG/HE PCs, and
approx. 1,200 words for CQM1H-series PCs.
The equation for maximum data link I/O response time is as follows:
Note If the total number of data link words is greater than the maximum number of
words that can be exchanged per data exchange, the maximum data link I/O
response time will be cycle time of PC at node #7
×
3.
In case of the CQM1H, however, the cycle time will be incremented by the
value obtained from dividing the total number of data link words by the maxi-
mum number of words (1,200 words) per time.
For example, if the total number of data link words is 5,000, the result will be
as shown below.
5,000/1,200 = 2.5 (approx. 3)
Cycle time of PC at node #7
×
(2+3)
Noise may increase I/O delays.
Case 3
The following diagram illustrates the data flow that will produce the maximum
data link I/O response time when the cycle time of the PC at node #1 < the
communications cycle time and the cycle time of the PC at node #7
≥
the
communications cycle time.
Input ON delay 1.5 ms
Cycle time of PC at node #1
×
2 15 ms
×
2
Communications cycle time
×
3 9.9 ms
×
3
PC cycle time at node #7
×
2 (see note) 8 ms
×
2 (see note)
Output ON delay 15 ms
Total (data link I/O response time) 92.2 ms