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8. COMMNICATIONS USING DEDICATED PROTOCOLS
MELSEC-A
8.9.2
Reading data from
buffer
memory (ACPU common command)
esignation Methodl
St. No.
:
Station number
Designation in protocol 1 is shown below.
Buffer memory read command
Character area A
I
To designate the word length, the following conditions must be met:
puter
' .
Number of characters
=
(word length)
x
4
lesignation Example
I
1
5
word length
5
64
(Head address)
+
(word length)
-
1
c
maximum address
number (7FFH)
I
I
I
I
I
I
I
i
1-word data uses 4 characters.
To read 2-word data from buffer memory addresses 180H and 181H in the AJ71C24 of
station number "10".
(Message wait time is 0 msec)
I
Q
I
st,
No.
HIL
I
AJ71 C24
Designation of the buffer memory
address range to be read from
Check sum is calculated
within this range
.
PC
No.
H l L
Character area 8
I
PC
NO.
Computer
A
$
s
;
I
,
*
c
I
Buffer memow
,
f
data
,
,
1 1 1 1
1 1 1 1
I
st,
NO.
H l L H l L
E
N
Q
MI
Sf.
No.
HlL
I
AJ71C24
~~~d addrer.
(5 characters
(hexadecimal))
I I I
I
PC
No.
H I L
wa'L"me
E
T
X
o A
3ovflr
Word
Therefore, a <-word data
is
expressed
( 2 characters
in 4 digits (hexadecimal).
(hexadecimel))
I
H l L
I
Sum
check
code
H l L
Indicates that:
The content of buffer memory address 180H is ABCDH (-21555 in decimal)
The content of buffer memory address 181H is 1234H (4660 in decimal)
L!
S
X
0 2 .
F
F
16w.46n
&,4~
c
R
0 ~ 5 2 ~
4 6 x , M ~
o
. %
o
o
1
s
Check sum is calculated
within this range
iO~,Um,Jlu!&
T O A F F A B C O 8 t
~ l ~ , 4 2 m , 0 ~ , 4 + ~ ~ 1 1 ~ , 3 2 ~ , ~ ~ , 3 4 ~
E
2 3 4 T D 4
X
0 ) "
1 ~ , 3 1 n
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