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Communications Cycle Time Section 8-2
E: Total number of bytes in messages transmitted during the
communications cycle
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 cable
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
Total number of data link words: 8,000 words
Nodes that send messages: 2 nodes
Bytes in all messages sent: 2,012
× 2 bytes
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 × 8 + 320 × 2 + 4 × 4,024 + 3,290 = 104,746 (µs)
≅ 105 (ms)
8-2-2 Inactive Data Links
The following equations are used to calculate a communications cycle time
when the data link is inactive.
Wired Systems
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
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
Baud rate Equation
2 Mbps 600 × B + 110 × C + 320 × D + 4 × E + 2,290 (µs)
1 Mbps 1,150 × B + 150 × C + 360 × D + 8 × E + 2,690 (µs)
500 Kbps 2,260 × B + 230 × C + 440 × D + 16 × E + 3,490 (µs)