Mitsubishi Electric AJ71C24-S6 User Manual page 91

5.
HALF-DUPLEX COMMUNICATIONS USING THE RS-232C INTERFACE
MELSEC-A
.-
SD (send data)
.T.
RS (send request)
CS (clear to send)
.
C D (receive carrier
detect)
( 2 )
AJ71 C24 is set to
"
non-priority
".
Continue data transmission
. . RO
(received data)
D
Because AJ7lC24 is wl to %on-
pnoriv,
dafsfranrmirrion
is in-
tenrppted when the CD r i g m
External device
turns ON.
The following steps describe the operations performed by AJ71C24 at every
thing. The signal names are of the signals of the AJ71C24.
Data C
As described in ( I ) , turn ONIOFF the RS signal of the AJ71C24 and do data
transmission to the external device.
Note that 5) is different.
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 RS signal ON.
If the CD signal is ON, wait until it turns OFF. After the CD is turned
OFF, turn ON the RS signal.
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 data send, stop the data send.
Then, turn the RS signal OFF and perform data receive process-
ing. (This occurs when the AJ71C24 and an external device start
data transmission simultaneously.)
6) After transmission from the external device is completed, resend
all data from the beginning, or transmit data remaining after the
send interruption in 5).
*1 Data set at buffer address 110H is not transmitted
*2
Resend all data from the beginning, or transmit data remaining
after the send interruption according to the setting of buffer
address 11 1 H.
When (a) starting or during the data transmission to the external device and (b) if the DSR(DR)
signal of AJ71C24 turns OFF, interrupt data transmission until the DSR signal turns ON.