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8. COMMUNICATIONS USING DEDICATED PROTOCOLS
MELSEC-A
8.4.4
Control format
4
Description
To read data
from the PC
CPU to the
computer
To write data
from the
computer to
the PC CPU
Remarks
Control Protocol
Transmission sequence
No.
R
F
-
*
H L H
L
St.
No.
:Station number
-
I
J
or
-
Transmission sequence
H , L H , L
H ,
L
E
- -
(1)The sum check is enabled by DIP switch 21.
The sum check code only exists when the sum check is enabled by turning DIP switch 21 ON.
(2)The sum check is made for characters marked
"*"
in these diagrams.
(3) In these diagrams, the contents of "character area
A",
"character area 13". and "character area C
depend on the individual system.
For details, see the relevant sections. The contents of al
character areas are the same for all 4 formats.
A
U71C24
St
NL
H , L
S t
NO.
H , L
;
AJ7tC24
PC
No.
H, L
I ' I ' I ' I
PC
No.
H , L
St
NO.
H , L
C L
R
F
,
a m -
mand
H , L
PC
NO.
H , L
Merrage
waiftime
Character
area B
;
,
Character
areac
&
H , L
Sum
: " , " . "
H, L
, ,
,
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