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9-2 Required transmission time and communication delay time
[1] Required transmission time
This is the time required for the master station to complete communication with all stations, and is
determined by the number of connected stations with and the number of data items to transmit.
Transmission T operation cycle =
N : Total number of link points (value to be calculated by relay link bytes and register link bytes
8 points).
P : Number of connected stations (master + slave)
136 : 136 bits are used for station address and error check data on the communication format.
1250 : Transmission rate: 1.25M bits per second
2.5 : Inter-station wait time plus processing time to move to next station (unit : ms)
α : Communication recovery operation time
• When an error occurs at any station, the master station periodically treats the error.
α = 3.5 × number of error stations ms
16 : Time to maintain token bus. It can enter at random intervals.
[Example] In the case of two connected stations and 8 bytes of link points,
Transmission T operation cycle ＝
PC operation
cycle
Master station
(PC00)
Slave station
(PC01)
Note: Data exchange time between a PC and the JW-21MN can be obtained by the following
formula:
When the control module is JW-31CUH1/32CUH1/33CUH1/33CUH2/33CUH3,
0.5 ms + 0.5μs x number of bytes to transfer.
(When the number of bytes to transfer is maximum (2304 bytes), 0.5 ms + 0.5μs x 2304 =
1.65 ms)
N + 136 × P
1250
8 bytes×8 points×2 stations + 136×2 stations
+ 2.5 × 2 stations + 16 = 21.32 ms
I/O processing
PC operation
Data exchange Note
Ｔ
9-3
α
+ 2.5 × P +
+ 16 (ms)
1250
I/O processing
Data exchange
: Send
: Receive
PC operation
9
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