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Data Link I/O Response Time Section 8-3
CVM1, CV-series, CS/CJ-series PLCs Under Synchronous Operation or C200HX/HG/
HE and CQM1H-series PLCs
Maximum I/O Response
Time
The maximum data link I/O response time is calculated for four cases.
Case 1
The following diagram illustrates the data flow that will produce the maximum
data link I/O response time when the cycle time of the PLC at nodes #1 and 7
are greater than the communications cycle time.
There are four points shown in the diagram above where processing is
delayed, increasing the data link I/O response time.
1,2,3... 1. The input arrives in the PLC just after I/O refreshing, causing a delay of up
to one cycle before the input is read into the PLC.
2. Data exchange occurs just after the PLC 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. At node #7, data from the previous data exchange is still being transferred,
causing a delay of up to one cycle before the input is read into the PLC.
4. The data transferred in data link processing arrives at the PLC at node #7
after data exchange, so the data will not be read into the PLC until the next
data exchange, causing a delay of up to 1 to 2 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 PLCs, approx. 3,700
words for CVM1 and CV-series PLCs, approx. 4,000 for C200HX/HG/HE
PLCs, and approx. 1,200 words for CQM1H-series PLCs.
Input device
Program
Program
Input
Input ON delay
1 cycle
Output
Output device
Output ON delay
1 cycle
Communications
cycle time
Data link transmission
Controller Link Unit
transmission processing
PLC at node #7
(1)
I/O refresh
Data exchang
e
Controller Link Unit
transmission processing
PLC at node #1
Previous communica
tions cycle data
Data link I/O response time
X
X
X
X
(2)
(3)
(4)
X