Data Exchange Timing - Omron SYSMAC LINK C1000H-SLK21-V1 System Manual

Data Link Characteristics
Changing the Communications Cycle Time
Example Calculations

5-10-2 Data Exchange Timing

Note Data links might not operate correctly if the communications cycle time is set to a
value shorter than that generated automatically by the system.
When the communications cycle time is generated automatically, it can be
changed by changing the other network parameters at the SSS/CVSS. The
default values and setting ranges of the other network parameters are shown in
the table below.
Network parameter
Maximum node number
Number of polled units
Maximum number of frames
Use the following formulae to calculate the change in the communications cycle
time that results from a change in other network parameters. A positive result
indicates the communications cycle time has been decreased and a negative
result indicates it has been increased. Round the result of the calculation to the
nearest millisecond.
Change of the communications cycle time (coaxial cable systems) =
(old maximum node number - new maximum node number) × 85 ms
+ (old maximum number of frames - new maximum number of frames) × 654 ms
+ (old number of polled units - new number of polled units) × 750 ms
Change of the communications cycle time (optical fiber cable systems) =
(old maximum node number - new maximum node number) × 111.5 ms
+ (old maximum number of frames - new maximum number of frames) × 770 ms
+ (old number of polled units - new number of polled units) × 750 ms
The examples below calculate the change of the communications cycle time for
both coaxial and optical fiber cable when the other network parameters are
changed as shown below:
Maximum node number:
Maximum number of frames:
Number of polled units:
Change of the communications cycle time (coaxial cable systems) =
(62 – 16) × 85 ms + (10 – 13) × 654 ms + (4 – 5) × 750 ms =
1.198 ms (1 ms after rounding)
Change of the communications cycle time (optical fiber cable systems) =
(62 – 16) × 111.5 ms + (10 – 13) × 770 ms + (4 – 5) × 750 ms =
2.069 ms (2 ms after rounding)
Note 1. If the maximum node number is set below the node number of any nodes in
the data link, those nodes will no longer be part of the data link.
2. If the maximum number of frames is set too low, errors might occur during
execution of events such as SEND(90) and RECV(98) instructions, inter-
node echo tests, and remote monitoring.
3. Lowering the number of polled units will increase the delay between reset-
ting a Unit or turning on its PC's power and its entrance into the network.
Data exchange takes place at the end of the cycle during CPU Unit servicing for
the SYSMAC LINK Unit, as indicated by the shaded areas in the diagrams. Data
exchange is limited to maximum of 1,642 words per cycle.
Default value
62
4
10
. . . . . . Changed from 62 to 16
. . Changed from 10 to 13
. . . . . . . Changed from 4 to 5
Section 5-10
Setting range
2 to 62
1 to 62
5 to 255
65