Mitsubishi Electric AJ71C24-S6 User Manual page 89

5. HALF-DUPLEX COMMUNICATIONS USING THE RS-232C INTERFACE
MELSEC-A
5.4.2
Data transmission timing from an AJ71C24
When doing half-duplex communications, data transmission timing from an
AJ71C24 is shown by using the CD signal and RS signal of the AJ71C24.
Control the CD signal of the AJ71C24 by setting the buffer memory of the
AJ71C24 to "prioritylnon-priority at simultaneous transmission" for data trans-
mission.
(1) AJ71C24 is set to
"
priority ".
Data
G 1
Stop the data send
Resend
lranrmiuion ircanlinued.
. -
SO (send data)
RS
(send request)
--
CS
(clear
to
send)
. -
CO (received carrier
- .
RD (received data)
The following steps describe the operation at every timing mentioned by (1)
to (6) in the above figure.
The signal names are of the signals of the AJ71C24.
As described in (1). turn ONIOFF the RS signal of the AJ71C24 with the
external device and transmit data to the AJ71C24.
1) When not transmitting data from the external device t o the
AJ71C24, turn the RS signal OFF.
2) When doing a data send, check the CD signal. If the CD signal is
OFF, turn the CD signal ON.
When the CD signal is ON, wait until it turns OFF. After the CD is
turned OFF, turn the RS signal ON.
3)
After turning the RS signal ON, transmit data.
4) After completing the data send, turn OFF the RS signal.
5) If the CD signal turns ON during the data send, continue transmit-
ting data send to the AJ71C24. (This occurs when the AJ71C24
and the external device start data transmission simultaneously.)
6) Transmit all interrupted data from the external device to the
AJ71 C24 after data send from the AJ71 C24 is completed.