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APPENDICES
MELSEC-A
APPENDIX 4
DC CODE CONTROL
This section explains DC code control done by the OS of an AlSJ71 C24 when
the DC code control is specified in the send control specification area (buffer
address 11AH) of an AlSJ71C24. This control operation can be executed at
data receive in the no-protocol/bidirectional mode using the RS-232C of the
A1 SJ71 C24.
The figures in this section assume a no-protocol mode.
A control code (ENQ, ACK, NAK, check sum, and error code) is included
in
the bidirectional mode data.
4.1
DCl/DC3
Send
Control
(1)
DCl/DC3 is used to inform an external device whether DC1 and DC3
have been received.
(2)
The control data is the same as the DTR control shown in Appendix
5.
An AlSJ71C24 transmits DC1 or DC3 t o the external device instead of
turning the DTR signal ON and OFF.
The DTR control of Appendix
5
gives details about send timing of DC1
and DC3.
The DTR signal ON or OFF signals are expressed as follows in this
manual.
(The DTR control)
(DC1 lDC3 control)
DTR signal OFF
- -
DC3 transmission
DTR
signal ON
- -
DC1 transmission
(3) DCl/DC3 send control can only be done using full-duplex communica-
tions.
(4)
Do not include DCl/DC3 in the send data specified by the user.
(5) When an OS receive area cannot store received data, until storage of
that received data is enabled, that received data is ignored.
External device
I
Data
I
I I
(Data is stored)
(Data storage)
304 bytes
After completing
the
read from
thesequenceprogram
APP
-
4
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