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10. COMMUNICATIONS IN THE BIDIRECTIONAL MODE
MELSEC-A
ixamole 2 Check
sum
disabled.
in
bvte units (receive memory area allocation: default)
/
'0
store "AJ71C24', received from a computer, to D O to D4 of a PC CPU. (AJ71C24 I/O ad-
Iress: 80 to 9F)
I
E
I
I
I
I
1
,
Computer
N
0007H
A
j
J
1
7
1
I
1
c
1
2
:
4
0
, , , , , ,
0 5 % 0 7 1 , W ~ 4 1
~ / 4 ~ ~ 1 3 7 ~ / 3 1 * / 4 3 ~ 1 3 2 ~ / 3 + ~ \
AJ71
M4
Data area
Received data read request
X81
Received
data length
Received data read completed Y91
is stored
PC CPU (program)
FROM
processing
(PC
CPU program example)
\ ' Y ' /
memory
Sequence program
data memory
Even if send data units are set to byte units, the FROM instruction in a
sequence program operates in word units. Therefore, the received
data length 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).
*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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