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8. COMMNICATIONS USING DEDICATED PROTOCOLS
MELSEC-A
8.9.3 Writing data to buffer memory (ACPU common command)
esignation Method]
St. No.
: Station number
Designation in protocol
1
is shown below.
To designate the word length, the following conditions must be met:
1
5
word length
5
64
*(Head address)
+
(word length)
-
1
c
maximum address numbf
(7FFH)
Write to buffer memory command
\ .
Character
area
C
lesignation Example1
To write 3-word data to buffer memory address 3AOH to 3A2H in the AJ71 C24 of station
number
"15".
(Message wait time is 0 msec)
Computer
E
;
Check sum is calculated within this range
AJ71 C24
Designation of the buifer memory address
range where data is to be written
E
Computer
l o
I
: : ,
HlL
AJ71 C24
A
Indicates that:
ABCDH (-21555 in decimal) is written to buffer memory address 3AOH
1234H (4660 in decimal) is written t o buffer memory address 3A1 H
2
6789H (26505 in decimal) is written to buffer memory address 3A2H
I C ~ . B ~ , < ~
I
L : ,
HlL
Number of characters
=
(word length) x 4.
HlL
I
St.
NO.
,
,
,
~ ~ , + 5 .
I
C
W
I
H I L
I
PC
NO.
1-word data uses 4 characters.
Therefore,
a
1-word data is expressed
in 4 digits (hexadecimal).
O M , I I ~
: : i s l f z
jir~.,3n5j.l,41~,jil
I
I
I
I
Head
I5 characters
(heradecimal))
1 1 1 1
N
~
F
F
F
C
W
O
O
O
~
A
~
O
~
A
B
C
D
~
~
~
~
~
N N I J M
I
Word
(2 characters
(hexadecimal))
I
0 ~ , 1 2 ~ , < ~ ~ , 1 1 ~ / 3 1 ~ ~ 2 ~ , ~ ~ , ~ ~ / j b l , ~ l ~ , j l ~ , 3 l ~
1
1
1
,
1
1
1
1
,
I
/
/
Data to
b e
written
to
buffer memory
I
N
,
1 1 1 1 1 1 1 I
I
I
I I
4 5 1 , ~ ~
I
s u m
check
code
H I L
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