Active Data Links - Omron SYSMAC 3G8F5-CLK11-E Operation Manual

Communications Cycle Time

9-2-1 Active Data Links

Calculation Example
160
The following equations are used to calculate the communications cycle time
when data links are operating. (The communications cycle time will vary some-
what depending on the baud rate and the conditions at that particular time.)
Wired Systems
Baud rate
2 Mbps 10 A + 600
1 Mbps 18 A + 1,150
500 Kbps 34 A + 2,260
Optical Systems
Baud rate
2 Mbps 10 A + 1,300
(Fixed)
Note The meanings of the variables in the above formulas are as follows:
A: Total number of data link words within the network
(total number of words in send areas of all nodes)
B: Number of polled nodes per comm cycle
(value specified in the network parameters)
C: Number of nodes connected to the 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 Optical Fiber Cable
connections. F = 7
Communications conditions are as follows:
Baud rate:
Network parameters:
Max node address:
Polled nodes per comm cycle:
Event-frames per comm cycle: 35
Network configuration:
Total number of data link words: 8,000 words
Nodes that send messages:
Bytes in all messages sent:
In this example, A to E in the equation have the following values.
A: 8,000
B: 4
C: 8
D: 2
E: 4,024
The communications cycle time is thus as follows:
10 8,000 + 600 4 + 290
≅ 105 (ms)
Equation
B + 290 C + 320 D + 4
B + 370 C + 360 D + 8
B + 530 C + 440 D + 16
Equation
B + 290 C + 320 D + 4
L µs (L is the cable length in km.)
2 Mbps
Defaults
32
4
8 nodes
2 nodes
2,012 2 bytes
8 + 320 2 + 4 4,024 + 3,290 = 104,746 (µs)
Section 9-2
E + 3,290 (µs)
E + 3,770 (µs)
E + 4,730 (µs)
E + 2 x F+ 3,290 (µs)