Inactive Data Links - Omron SYSMAC 3G8F7-CLK12-E Operation Manual

Communications Cycle Time

8-2-2 Inactive Data Links

Calculation Example for
Wired Networks
118
The following equations are used to calculate the communications cycle time
when the data links are inactive. (The communications cycle time will vary some-
what depending on the baud rate and the conditions at that particular time.)
Wired Networks
Baud rate
600 × B + 110 × C + 320 × D + 4 × E + 2,290 (µs)
2 Mbps
1,150 × B + 150 × C + 360 × D + 8 × E + 2,690 (µs)
1 Mbps
2,260 × B + 230 × C + 440 × D + 16 × E + 3,490 (µs)
500 Kbps
Optical Ring Networks
Baud rate
2 Mbps Token Ring Mode
1,740 × B + 450 × C +1,100 × D + 4 × E + 2 x F + 3,000 (µs)
(fixed)
Token Bus Mode
1,300 × B + 110 × C + 320 × D + 4 × E + 2 x F + 1,800 (µs)
Note B: Number of polled nodes per communications cycle
(value specified in the network parameter)
C: Number of nodes connected to network
D: Number of nodes that send messages during the
communications cycle
E: Total number of bytes in messages transmitted during the
communications cycle
F: Extra communications time for long-distance cable connections.
If L is the cable length in km, then F = 7 × L µs for H-PCF cable and
F = 5 × L µs for GI cable.
Communications conditions are as follows:
Type:
Transmission medium:
Baud rate:
Network parameters:
Max node address:
Polled nodes per comm cycle:
Event-frames per comm cycle: 35
Network configuration:
Nodes that send messages:
Bytes in all messages sent:
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 (µs)
≅ 22 (ms)
Section
Equation
Equation
Wired
Twisted-pair cables
2 Mbps
Defaults
32
4
8 nodes
2 nodes
2,012  2 bytes
8-2