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10. COMMUNICATIONS IN THE BIDIRECTIONAL MODE
MELSEC-A
-
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Example 2 Check sum disabled. i n bvte units (receive memorv areaallocation: d e f a u x p
T o store "AlSJ71C24", received from a computer, to DO to D4 of a AISCPU. (AlSJ71C24 I/O
3ddress: 80 to 9F)
Received data read request
X81
Received data read completed Y91
A1 SCPU (program)
A1 5171 C24
Sequence program
buffer memory
data memory
POINTS]
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, 9 bytes of data must be converted into 5 words
(9
+
2
=
4.5
...
5).
I
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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