Omron SYSMAC CS/CJ Series Programming Manual page 264

Cycle Time/High-speed Processing
Using DLNK(226)
Input
Input ON delay
×
DLNK
Data transfer to
Controller Link Unit
1,2,3...
Output ON delay
Total (data link I/O response time)
The following diagram illustrates the data flow that will produce the maximum
data link I/O response time when DLNK(226) is used.
Input Unit
(1) Delay of 1.5 cycle times
One cycle time
Program
execution DLNK
×
One com-
munica-
tions cycle
Processing in
CPU Unit #2
Output Unit
Output ON delay
Maximum data link I/O response time
There are three points shown in the diagram above where processing is
delayed, increasing the data link I/O response time.
Note In this example, it is assumed that DNLK(226) is placed after other instruc-
tions in the program in both CPU Units
1. The input arrives in the PLC (CPU Unit #1) just after I/O refreshing, caus-
ing a delay of one cycle before the input is read into the PLC. CPU Bus
Units are refreshed during program execution, reducing the total delay to
approximately 1.5 cycle times.
2. Data exchange occurs just after the PLC passes the token that makes it
the polling node, causing a delay of up to one communications cycle time
before the data is transferred in data link processing. There will also be a
delay of up to one communications cycle time after receiving the token,
causing a total delay of up to two communications cycle times.
3. The data transferred in data link processing arrives at the PLC (CPU Unit
#2) after the I/O refresh, but DLNK(226) refreshes the data, so the data will
be read into the PLC without causing a delay of up to one cycle. The Basic
I/O Units are refreshed after program execution, causing a total delay of
approximately one cycle time.
15 ms
126.5 ms
DLNK(226) execution
Processing in
DLNK
CPU Unit #1
(2) Delay of two communications cycle times
One cycle time max
(3) Delay of approx one cycle time
×
Data received from Controller Link Unit
Program
DLNK
DLNK
execution
Section 6-1
Basic I/O Units refreshed.
CPU Bus Units refreshed
(including data links)
Data link transmissions
DLNK
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