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COMMUNICATIONS USING DEDICATED PROTOCOLS
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MELSEC-A
8.6
Character Area Data
Transmission
The concept of transmission data handled as character areas when using
commands to carry
out
data communications between
the
computer and the
PC
CPU
is explained in this section. The data shown in the examples is
contained in character area
8
in
the case of read and monitor, and in
character area
C
in
the case of write, test, and monitor data register.
(1)
Bit device memory read and write
The bit device memory can be handled in bit units
(1
device point) or
word units
(16
device points).
These units are described below.
(a) Bit units
(1
point)
When the bit device memory is handled as bit units, the specified
number of device points from the specified head device in sequence
from the
left
are represented as
1
(31H)
if
the
device is ON, or
0
(30H)
if the device is
OFF.
Example: Indication of the ON/OFF status of
5
points from MlO
WiW
M14
is
ON
Indm
tM
M13
ir
OFF
Withd
M12
ir
ON
lndicatrrthatM11
kOFF
Indim
tiut
M10
i8
ON
(b) Word units (16 points)
When the bit device memory is handled as word units, each word
is expressed sequentially
in
hexadecimal values
in
4-bit units from
the higher
bit.
Example: Indication of the ON/OFF status of
32
points from M16
N~bWdd&riCOpoiIVbk~"~
memory
is
uaod
in
units
d
word.
m;m
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IIII
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poinb
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M001802AB12134CD
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Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
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