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195
Communications Cycle Time
Section 8-2
The network parameters become valid immediately after being set.
Note
1.
Always stop the data link before changing network parameters.
2.
Specify a value for the maximum node address that is equal to or greater
than the maximum node address in the Controller Link Network.
3.
For the CVM1 and CV-series PCs, always set the System Protect Key
Switch on the CPU Unit to NORMAL. Otherwise, the network parameter
settings will not be stored normally.
8-2
Communications Cycle Time
This section describes how to calculate the communications cycle time.
8-2-1
Active Data Links
The following equations are used to calculate the communications cycle time
when data links are operating.
Wired Systems
Note 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
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
Baud rate
Equation
2 Mbps
10
×
A + 600
×
B + 290
×
C + 320
×
D + 4
×
E + 3,290 (
µ
s)
1 Mbps
18
×
A + 1,150
×
B + 370
×
C + 360
×
D + 8
×
E + 3,770 (
µ
s)
500 Kbps
34
×
A + 2,260
×
B + 530
×
C + 440
×
D + 16
×
E + 4,730 (
µ
s)
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
Summary of Contents for CVM1-CLK21
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