1.
GENERAL DESCRIPTION
MELSEC-A
Compared with the AJ71 C24-S3 and AJ71 C24-S6 computer link modules,
the AJ71C24-S8 supports the following six additional functions:
[(l)
to
(6)
are the additional functions when compared with the
AJ71
C24-S3]
(1)
Commands dedicated for use with the A2ACPU(Sl) and A3ACPU:
All memory devices of the A2ACPU(S1) and A3ACPU (the AnACPU
in
this manual) are accessible using these dedicated commands.
(2) Data transmission
in
the bidirectional mode:
This feature allows the AJ71 C24-S8 to interface
1
:l
data communica-
tions using the ACK code between a PC CPU and a computer.
When data is transmitted from the AJ71 C24-S8 to a computer, a control
code
ENQ,
the data length code, and a check sum are added respec-
tively to the beginning, the middle, and the end
of
the send message.
(The check sum is optional.)
When the AJ71C24-S8 receives data from a computer,
it
transmits a
control code ACWNAK back to the computer. This indicates the result
of the receive (normal/abnormal).
The AJ71 C24-S8 thus adds the
ENQ
code, data length, and check sum
and checks
the
reception of the response message at the data trans-
mission.
It
checks the received data and sends the response message
after
it
received data.
The length
of
a data communications sequence program can be shor-
tened by using the bidirectional mode.
(3) The communications mode using
the
RS-232C interface can be set to
either full-duplex or half-duplex:
The communications mode using the RS-232C interface of the
AJ71 C24-S8 can be switched either to full-duplex or half-duplex accord-
ing
to the specifications of the peripheral device.
(4) Multidrop link
with
more than one computer is possible:
More than one computer can be put into a multidrop link with the
AJ71 C24-S8.
The PC CPU modules
in
the multidrop link can
be
accessed from the
computers for read/write of device data and sequence programs.
1-2
c
c
Ir
c
L
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