9.
COMMUNICATIONS
IN
THE
NOIPROTOCOL
MODE
MELSEC-A
9.
COMMUNICATIONS
WITH
A COMPUTER
IN
THE
NO-PROTOCOL MODE
Read this section
if
the
RS422
and
RS-232C
interfaces are used with the
dedicated protocol
in
the no-protocol mode by (a) setting the
AJ71C24
mode setting switch at any position from
1
to
8,
or (b) using the mode
switching function to set any mode number from
1
to
9.
If these interfaces are used with the dedicated protocol
in
the bidirectional
mode,
it
is not necessary to read this section.
9.1
Bdc8
of
the
No-Protocol
Mode
(1)
What no-protocol mode means
In
no-protocol communication:
0
Data written to the no-protocol
AJ71C24
send area (in buffer memory)
using the
TO
instruction
in
a sequence program is output to an
external device in the same code.
*Data received from an external device is read from the no-protocol
AJ71 C24
receive area (in buffer memory) using the
FROM
instruction
in a sequence program.
Write
cw
(TO
inrtnrdion)
mw
OOHto
FFH
'
pwm
Re8d
-------
In
the no-protocol mode, data
is
not converted to
ASCII
code in the
AJ71C24.
If
ASCII
code
is
required, data must be processed into
ASCII
code
in
a
PC CPU
or external device.
(2)
Designating a word/byte unit for no-protocol mode communication
For data communications
in
the no-protocol mode, a unit of data to be
transmitted may be selected between words and bytes. Defautt setting
for data unit selection is "word", but selection is possible by writing
'1"
or
"0"
to address
103H
in
the buffer memory area.
(Section
7.4.3
gives details about the program to make this setting.)
9-1
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