1.
INTRoDuCTtoN
/MELSEC-A
1.1.2
Data
communication
betweem
the
A2CCPU
ad
the remote terminal module
(1)
Maximum number of remote terminal modules to be con-
nected
A maximum of
14
remote terminal modules can be connected
to the A2C.
(2)
Data communication with remote terminal modules
(a) Perform the following initial setting.
1)
The first station number of the remote terminal module
2)
Protocol
See Section
4.2.9
for details of initial setting.
(b) Execute data communication with the
FROM0
instruc-
tion.
See the ACPU Programming Manual (Common Instruc-
tions) for details of the FROM/TO instruction.
(b)
Transmission
of
designated data
by
executing TO instruction
CPU
I
A
MINI-S3
link
Remote
terminal
n
7-
Station number:
9
U
I
Station number: n Station number:
5
complete signal
Data communication with the remote terminal module is executed
as
described below.
(a)
The
FROM/TO
and PRC instructions are executed by the sequence program.
(b) The request to send designated data
or
the data is transmitted by executing the
FROM/TO
instruction after executing the PRC instruction.
1)
At
FROM
instruction execution
:
Data send request
2)
TO instruction
:
Data sending
A2C.
signal from the remote terminal module.
(c) The remote terminal module sends the completion signal of data send or receive to the
(d) The A2C turns
ON
the complete signa.1
(Ml)
when
it
received the sendreceive complete
Fig.
1.2
Data
Communhtion
between
the
Ax
and
the
Rmote
Terminal
Module
(3)
Response time
Communication of
8
data with one
FROM/TO
instruction
requires approximately
400
ms (when scan time is 100 ms).
1
,?
1
1
1
1
I
1
I
4
"I
.-
1
3
I
7
1
i.1
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