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8.
COMMUNICATIONS USING DEDICATED PROTOCOLS
MELSEC-A
8.1
4.3
On-demand function designation
esignation Methodl
Designation in protocol 1 is shown below.
AJ71C24 adds these fields of data
\ I
TO
PC C P U / ~ p r o c e s s ~ n g
The following is written to AJ71C24 buffer memory:
1 0 9 H
...
Head address of transmission data storage area
lOAH
...
Data length
Computer
. L
L
:I) Buffer memory area 100H to 11FH is the special applications area.
Do not use this area to store the data to be transmitted with
the on-demand function.
(2) Data length setting range must meet the following criteria:
When the buffer memory area of OH to FFH is used:
(Head address)
+
[(data length)
-
1 ]
5
FFH
When the buffer memory area of 120H to 7FFH is used:
(Head address)
+
[(data length)
-
I ]
5
7FFH
(3) The AJ71C24 appends "FE" as the PC CPU number.
(4) The block number is "OOH" when protocol 2 is used.
I
The on-demand function may be used only when the system configura-
tion is a 1 : l ratio of computers to PC CPUs.
1
s u m
check
code
H I L
AJ71 C24
If the on-demand function is used in a multidrop link system of 1:n. 2:n,
or m:n ratios, communications data in control protocols 1 to 4 and
on-demand transmission data will be destroyed and correct data trans-
mission is precluded.
\
S
;
I
station.
Number
H
L
I
PC
H I L
Se"ddata
E
T
X
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