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9. COMMUNICATIONS IN THE NO-PROTOCOL MODE
MELSEC-A
:xample 2: By receiving the set length of data, in byte units (receive area allocation defaul
To receive "AJ71C24" from an external device and t o store it t o DO to D4 of PC CPU with tt
following setting. (AJ71C24 I10 address: 80 to 9F)
I
,
,
,
,
,
A 1
J
87%
1
l
C N
2 1
4
I
I
I
I
I
7
bytes
'!.;2~.:,,;,,.:',~:,2":%~
-
\
AJ71 C24
\\
\
\
Received data read request
X81
Received
data length
is stored
Received data read completed Y91
PC CPU (program)
PC CPU program example
I
memory
*Even if transmission data units are set t o byte units, the FROM
instruction in a sequence program operates in word units. Therefore.
the length of receive data must be converted to the number of buffer
memory points (word units).
In the above example, 7 bytes of data must be converted into
4
words
(7
+
2
=
3.5
...).
a
When an odd number of bytes of data is received, the higher 8 bits of
the last address read by the FROM instruction are "OOH".
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