Sharp JW-20CM User Manual page 110

9-3 Data transfer required time and communication delay
time
(1) Required time for data transfer
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.
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 =
9
PC operation
cycle
Master station
(PC00)
Slave station
(PC01)
N + 136 × P
α = 3.5 × number of error stations ms
8 bytes×8 points×2 stations + 136×2 stations
+ 2.5 × 2 stations + 16 = 21.32 ms
I/O processing
Data exchange
Ｔ
+ 2.5 × P + α + 16 (ms)
1250
1250
PC operation
: Send : Receive
9 12
·
I/O processing
PC operation
Data exchange