Omron CS1W-CLK12-V1, Operation Manual

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190
Data Link I/O Response Time Section 9-3
Network configuration: 8 nodes
Nodes that send messages: 2 nodes
Bytes in all messages sent: 2,012
×
2 bytes
In this example, A to D in the equation have the following values.
A: 4; B: 2; C: 8; D: 7
×
8
The maximum communications cycle delay in token-ring mode would be as
follows:
(4
×
4 + 2
×
2 + 1)
×
(3
×
8 + 7
×
8) = 1,680 (
µ
s)
≅
1.7 (ms)
The rate of change in the communications cycle time when data links are
active would be as follows (refer to 9-2-1 Active Data Links):
(111 + 1.7)/111
×
100
≅
101.5 (%)
The rate of change in the communications cycle time when data links are
inactive would be as follows (refer to 9-2-2 Inactive Data Links):
(32 + 1.7)/32
×
100
≅
105.3 (%)
9-3 Data Link I/O Response Time
When accurate communications timing is required, you need to understand
data exchange timing and the time required for data transmission and recep-
tion via data links. Use the information described in this section as reference
information for system construction.
9-3-1 Data Exchange Timing
This section describes data exchange timing for data links between the Con-
troller Link Unit and the PLC’s CPU Unit. Data exchange is executed as inter-
rupt processing during CPU Bus Unit or Programming Device/Host Link
servicing performed by the CPU Unit. This interrupt processing is executed
each time data exchange between the local node and each node connected
via a data link is completed.
Data exchange timing differs depending on the CPU Unit model and the CPU
Unit the Execute Process (asynchronous or synchronous) specified in PLC
Setup, as described below.
CVM1 and CV-series PLCs
Under Asynchronous
Operation When a CVM1 or CV-series CPU Unit is operating in asynchronous mode,
data exchange with the Controller Link Unit is executed as interrupt process-
ing during peripheral processing, regardless of the cycle time of PLC instruc-
tion execution. Data exchange timing is as follows:
More than one data exchange can be executed during a PLC cycle, depend-
ing on the data exchange timing. If interrupt processing for data exchange is
executed, the peripheral servicing interval will be lengthened by the time
required for the interrupt processing (see 9-3-2 Data Processing Time on
page 191).
Instruction execution
PLC cycle time
Execution
I/O refreshing
PLC processing
Peripheral processing
Peripheral servicing interval
Basic processing
CPU Bus
Unit service
Programming
Device/Host Link
service
Interrupt processing
for data exchange
Execution Execution
I/O refreshing I/O refreshing
Interrupt processing
for data exchange Interrupt processing
for data exchange
Basic processing
CPU Bus
Unit service
Programming
Device/Host Link
service
CPU Bus
Unit service
Programming
Device/Host Link
service
Basic processing