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257
Data Link I/O Response Time
Section 8-3
The number of bytes in each message differs according to the instruction
being issued.
Calculation Example
Communications conditions are as follows:
Transmission medium:
Twisted-pair cables
Baud rate:
2 Mbps
Network parameters:
Defaults
Max node address:
32
Polled nodes per comm cycle:
4
Event-frames per comm cycle:
35
Network configuration:
8 nodes
Nodes that send messages:
2 nodes
Bytes in all messages sent:
2,012
×
2 bytes
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 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.
Instruction
When sent
When received
SEND
Number of words to be sent
×
2
+ 18
14
RECV
18
Number of words to be
received
×
2 + 14
CMND
Number of bytes in command
data + 10
Number of bytes in response
data
Summary of Contents for C200HW-CLK21
Page 3: ...iv ...
Page 9: ...x ...
Page 12: ...xiii TABLE OF CONTENTS Index 367 Revision History 373 ...
Page 13: ...xiv ...
Page 19: ...xx ...
Page 57: ...32 Application Precautions Section 1 5 Example CX Programmer Response Timeout Setting ...
Page 69: ...44 Message Service Procedure Section 2 2 ...
Page 111: ...86 Constructing Networks with Repeater Units Section 3 4 ...
Page 154: ...129 Setting Data Links Section 5 2 Device Information Setting Data Link Tables ...
Page 261: ...236 Response Codes Section 6 7 ...
Page 297: ...272 Message Delay Times Section 8 4 ...
Page 353: ...328 Handling Precautions Section 9 6 ...
Page 364: ...339 Changing the Data Link Tables with Active Data Links Section 10 2 ...
Page 365: ...340 Changing the Data Link Tables with Active Data Links Section 10 2 ...
Page 369: ...344 Standard Models Appendix A ...
Page 391: ...366 Using the Relay Terminal Block Appendix C ...
Page 397: ...372 Index ...
Page 401: ...376 Revision History ...