Flow Control - Mitsubishi MELSEC AJ65BT-R2 User Manual

8 OTHER FUNCTIONS

8.3 Flow control

This function notifies the partner device whether the local station can receive data.
•
When R2 is receiving data
Whether to cancel/restart transmission to the R2 is notified to the external device
according to the amount of space open in the R2 OS reception area.
• When R2 is transmitting data
The transmission from the R2 is canceled/restarted according to the requests from
the external device.
The cancel/restart is notified with the DC code control or DTR (ER)/DSR (DR) signal
control (hereinafter DTR/DSR signal control).
(1) DC code control
The R2 notifies the external device whether the local station can receive data by
transmitting DC1, DC3. Whether the external device can receive data is
confirmed by receiving DC1, DC3.
(a) DC1/DC3 transmission control
If the amount of space open in the OS reception area is less than 64 bytes,
the R2 transmits DC3 to the external device, and the external device
cancels the transmission to the R2.
When the reception data is read out from the programmable controller CPU
and the amount of space open in the OS reception area reaches 263 bytes
or more, DC1 is transmitted to the external device, and the transmission
from the external device to R2 is restarted.
External device side
R2 side
(OS reception area)
5120
bytes
Data
D
C
3
R2
(Data storage)
Open area 64 bytes
or less
Reading of reception data by programmable controller CPU
8 - 6
MELSEC-A
D
C
1
R2
(OS reception area)
(Data storage)
5120
bytes
Open area
Data
263 bytes
or more