Omron CVM1-CLK21, Руководство по эксплуатации

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197
Data Link I/O Response Time Section 8-3
In this example, B to E in the equation have the following values.
B: 4
C: 8
D: 2
E: 4,024
The communications cycle time is thus as follows:
600
×
4 + 110
×
8 + 320
×
2 + 4
×
4,024 + 2,290 = 22,306 (
µ
s)
≅
22 (ms)
8-3 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.
8-3-1 Data Exchange Timing
This section describes data exchange timing for data links between the Con-
troller Link Unit and the PC’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 PC
Setup, as described below.
CVM1 and CV-series PCs
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 PC instruc-
tion execution. Data exchange timing is as follows:
More than one data exchange can be executed during a PC cycle, depending
on the data exchange timing. If interrupt processing for data exchange is exe-
cuted, the peripheral servicing interval will be lengthened by the time required
for the interrupt processing (see 8-3-2 Data Processing Time on page 198).
Instruction execution
PC cycle time
Execution
I/O refreshing
PC 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