8.
COMMUNICATIONS USING DEDICATED PROTOCOLS
I
j,"..,
,
a.
1..
MELSEC-A
8.4.5
Setting
protocd
data
(1) Control code
All
control codes are sent and received in hexadecimal. They are
shown in the following table.
NUL
1
OOH
I
Null
I
LF
I
OAH
I
Line Feed
I
End
of
I4 I
Negative
Acknowledge
I
MQ
OSH
Enquiry
G
47H Good
ACK
06H
Acknowledge
N
4EH
No Good
(a) The NUL code
(OOH)
is ignored in all messages.
If
a NUL code is
(b) In format
3,
control code
'GO"
is equivalent to
ACK
and 'NN" is
included in a message,
it
is processed as if
it
did not exist.
equivalent to NAK.
(c) After receiving an EOT or CL code, the AJ71 C24 initializes transmis-
sion but does not answer. The initializing code depends on the
format as indicated below.
At
this time there is no answer from the
AJ71 C24.
I
Format
1
to
3
I
Format
4
AJ71-4
(2)
Block number
The block number is an optional number assigned as a data reference
number for the computer. Block numbers are used to arrange data, etc.
Block numbers may be from
OOH
to
FFH
in
2-digit ASCII (hexadecimal).
8-
11
-
. .
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