Omron CVM1 Series, Operation Manual

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Appendix C
PC Link System I/O Response Time
Calculating the PC Link Transmission Time
Calculating the PC Link Cycle Time
The following diagram shows the PC Link’s cycle time.
PC Link cycle time = (T
N
×
Total number of PLCs in PC Link) + 10 ms
T
N
= Transmission time/Node
Example Calculation:
When there are 128 Link Relay bits/Unit and 8 Units are connected, T
N
= 2.8 ms.
PC Link cycle time = 2.8
×
8 + 10 ms = 32.4 ms
Calculating the Polling Sequence Processing Time
The link polling sequence, which is directed to nodes that have not yet joined the PC Link, is sent once every
256 PC Link cycles. Consequently the polling sequence cycle is 256
×
one PC Link cycle.
Polling sequence processing time = 15 ms
×
(n
−
m)
(n: max. number of connectable Units; m: number of Units joined into PC Link)
Minimum Transmission Time
Minimum transmission time = T
N
+ 10 ms
To determine the value of T
N
, refer to the table above.
T
N
Polling Unit
(Master)
Slave
Polling
Node 1
Slave data transfer
Processing time when data
transfer is completed = 10 ms
10 ms
Processing
One cycle's transmission time
Send Receive
Node 2 Node n
Number of Link bits/Unit 32 64 128 256 512
T
N
(ms) 2.2 2.5 2.8 3.8 5.8
PC Link
cycle
256 PC Link cycles
Polling
sequence
processing
Polling
sequence
processing