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11. TROUBLESHOOTING
MELSEC-A
11.3.3 When the neutral state does not change or data is not received
The AJ71C24 LED remains ON indicating (a) the neutral state, or (b) that
communications is disabled (even though a communications request is
made to the AJ71C24). The computer cannot receive data.
change.
and AJ71C24 settings
Mitsubishi
(see
Section 4.3.2).
I
NO
NO
1
I
3
(1) Check point *I
Make sure the AJ71C24 RD
signal line is connected to the
computer SD signal line.
Check the multidrop line
connection.
(2)
Check point *2
*Make sure the AJ71C24 SD
signal line is connected to the
computer RD signal line.
Check the multidrop line
connection.
Connect the signal line
(see Section 4.5).
Conned the signal line
(see Section 4.5).
NO
NO
I
I
Transmit data from the
YES
YES
computer.
Send data which
complies with the set
dedicated protocol.
RS422
RS-422
I I
NO
I
Either (a) set the CD signal
NO
so
that it is always
ON
during
full-duplex communications,
or (b) set the RS-23C CD
Keep the data terminal
ready signal
ON.
terminal check to 'disabled'.
Set the RS-B2C CD terminal
check to 'enabled' during
half-duplex communications.
Also, set the computer so
that the signal turns
ONIOFF
using the timing mentioned
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