IDEC MicroSmart - Manual (Page 418)

25: D ATA L INK C OMMUNICATION
25-10 « FC4A M ICRO S MART U SER ’ S M ANUAL »
The communication sequence in the separate refresh mode is shown below:
Refresh Time at Master Station for Communication with One Slave Station (Trf)
The master station requires the following time to refresh the transmit and receive data for communication with one slave
station.
[Baud Rate 19200 bps] Tr f = 4.2 ms + 2.4 ms
× (Transmit Words + Receive Words) + 1 scan time
[Baud Rate 38400 bps] Tr f = 2.2 ms + 1.3 ms
× (Transmit Words + Receive Words) + 1 scan time
Total Refresh Time at Master Station for Communication with All Slave Stations (Trfn)
The master station requires the following time to refresh the transmit and receive data for communication with all slave
stations, that is the total of refresh times.
[Baud Rate 19200 bps] Tr fn =
∑ Trf = ∑ {4.2 ms + 2.4 ms × (Transmit Words + Receive Words) + 1 scan time}
[Baud Rate 38400 bps] Tr fn =
∑ Trf = ∑ {2.2 ms + 1.3 ms × (Transmit Words + Receive Words) + 1 scan time}
Example: Refresh Time
When data link communication is performed with such parameters as transmit words 6, receive words 6, slave stations 8,
and average scan time 20 ms, then the total refresh time Trf8 for communication with all eight slave stations will be:
[Baud Rate 19200 bps] Tr f8 = {4.2 ms + 2.4 ms
× (6 + 6) + 20 ms} × 8 = 424.0 ms
[Baud Rate 38400 bps] Tr f8 = {2.2 ms + 1.3 ms
× (6 + 6) + 20 ms} × 8 = 302.4 ms
Master Station
1 scan time
END Processed
Slave 1
Refresh
Slave 1 Comm.
Completion M8080
Slave 2 Comm.
Completion M8081
Slave 31 Comm.
Completion M8116
All Slave Comm.
Completion M8117
1 scan
Communication
Completion M8080
END Processed
Slave Station 1
Master
Station
Slave
Station
1
1 scan time
Communication
Completion M8080
Slave Station 2 Slave
Station
2
1 scan time
Communication
Completion M8080
Slave Station 31
Slave
Station
31
END Processed
END Processed
Slave 2
Refresh Slave 3
Refresh Slave 31
Refresh Slave 1
Refresh