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9. COMMUNICATIONS IN THE NO-PROTOCOL MODE
MELSEC-A
9.3.2
Precautions during data communications
(1)
Conditions when the
AlSJ71 C24
transmission sequence is initialized
The transmission sequence is initialized in the following cases:
Power is turned ON or the
AlSCPU
is reset by the reset switch.
The
AlSJ71C24 CD
signal is turned OFF during
RS-232C
full-duplex
communications
If the
CD
signal is turned OFF during send or receive processing,
data being processed for transmission or the data stored in the
AlSJ71C24
receive data storing
OS
area is cleared.
In full-duplex communications, keep the
CD
signal ON.
The ONiOFF status of the
CD
signal is ignored if
"CD
terminal check
disabled" is set at
10BH
of the buffer memory address.
(2) FROMRO accesses to an
A1 SJ71 C24
The FROMITO accesses made by the
PC CPU
to an
AlSJ71C24
must
be executed only when they are strictly needed.
If a FROMITO access is made by the
PC CPU
to an
AlSJ71C24
when
the
AlSJ71C24
is transmitting data to an external device, the FROMITO
instruction is given priority in processing.
The data transmission time of the
AlSJ71C24
accordingly increases
since the FROMITO instruction is processed.
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