Omron CS1W-SLK11-21 - 06-2004 Manual page 80

Data Link Characteristics
Manual Generation
Note
Example Calculations
Note
Changing the Communications Cycle Time
When data link tables have been generated manually, the communications
cycle time can be set to a constant value or generated automatically.
The communications cycle time can be set as a constant from 5 to 255 ms in
increments of 1 ms using the Support Software to eliminate variations caused
by noise or other factors. When the communications cycle time is not set as a
constant, it will be generated automatically according to the equations below.
Round the result of the calculation to the nearest millisecond.
Communications cycle time (coaxial cable systems) =
Maximum node address × 0.085 ms + maximum number of frames
× 0.654 ms + number of polled units × 0.75 ms + number of Link Units
× 0.056 ms + total number of words × 0.01 ms + 1.322 ms
Communications cycle time (optical fiber cable systems) =
maximum node address × 0.1115 ms + maximum number of frames × 0.77
ms
+ number of polled units × 0.75 ms + number of Link Units × 0.056 ms
+ total number of words × 0.010 ms + 1.322 ms
The present and maximum values of the communications cycle time can be
monitored from the Support Software.
The examples below calculate the communications cycle time for both coaxial
and optical fiber cable with the following characteristics:
Maximum node address: . . . . . . 62
Maximum number of frames: . . . 10
Number of polled units: . . . . . . . 4
Number of Link Units . . . . . . . . . 32
Total number of words . . . . . . . . 2,000
Communications cycle time (coaxial cable systems) =
62 × 0.085 ms + 10 × 0.654 ms + 4 × 0.75 ms + 32 × 0.056 ms + 2000 ×
0.01 ms + 1.322 ms
= 37.924 ms (38 ms after rounding)
Communications cycle time (optical fiber cable systems) =
62 × 0.1115 ms + 10 × 0.77 ms + 4 × 0.75 ms + 32 × 0.056 ms + 2000 ×
0.01 ms + 1.322 ms
= 40.727 ms (41 ms after rounding)
Data links might not operate correctly if the communications cycle time is set
to a value shorter than that generated automatically by the system. If the LNK
indicator on the front of a CS-series SYSMAC LINK Unit (CS1W-SLK11/12)
flashes quickly (at approximately 100-ms intervals), either automatically set
the communications cycle time for the data link table, or manually set the
communications cycle time to a longer value.
When the communications cycle time is generated automatically, it can be
changed by changing the other network parameters on the Support Software.
The default values and setting ranges of the other network parameters are
shown in the table below.
Network parameter
Maximum node address
Number of polled units
Maximum number of frames
Use the following formulas to calculate the change in the communications
cycle time that results from a change in other network parameters. A positive
Default value
62 2 to 62
4 1 to 62
10 5 to 255
Section 4-11
Setting range
63