Rs232c line control signals, Rs232c line control signals -29 – IDEC MicroSmart User Manual
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17: U
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RS232C Line Control Signals
While the
MicroSmart
is in the user communication mode, special data registers can be used to enable or disable DSR and
DTR control signal options for port 2. Port 2 is available on the 16- and 24-I/O type CPU modules only, and an optional
RS232C adapter must be installed on the port 2 connector to enable the RS232C communication. The DSR and DTR con-
trol signal options cannot be used for port 1.
The RTS signal line of port 2 remains on.
Special Data Registers for Port 2 RS232C Line Control Signals
Special data registers D8104 through D8106 are allocated for RS232C line control signals.
Control Signal Status D8104
Special data register D8104 stores a value to show that DSR and DTR are on or off at port 2. The data of D8104 is updated
at every END processing.
DSR Control Signal Status in RUN and STOP Modes
DTR Control Signal Status in RUN and STOP Modes
RS232C Port
DR No.
Data Register Function
DR Value Updated
R/W
Port 2
D8104
Control signal status
Ever y scan
R
D8105
DSR input control signal option
When sending/receiving data
R/W
D8106
DTR output control signal option
When sending/receiving data
R/W
D8104 Value
DTR
DSR
Description
0
OFF
OFF
Both DSR and DTR are off
1
OFF
ON
DSR is on
2
ON
OFF
DTR is on
3
ON
ON
Both DSR and DTR are on
Communication
Mode
D8105 Value
DSR (Input) Status
RUN Mode
STOP Mode
User
Communication
Mode
0 (default)
No effect
No effect (TXD/RXD disabled)
1
ON:
Enable TXD/RXD
OFF: Disable TXD/RXD
No effect (TXD/RXD disabled)
2
ON:
Disable TXD/RXD
OFF: Enable TXD/RXD
No effect (TXD/RXD disabled)
3
ON:
Enable TXD
OFF: Disable TXD
No effect (TXD/RXD disabled)
4
ON:
Disable TXD
OFF: Enable TXD
No effect (TXD/RXD disabled)
5 or more
No effect
No effect (TXD/RXD disabled)
Maintenance Mode
—
No effect
No effect
Communication
Mode
D8106 Value
DTR (Output) Status
RUN Mode
STOP Mode
User
Communication
Mode
0 (default)
ON
OFF
1
OFF
OFF
2
RXD enabled:
ON
RXD disabled:
OFF
OFF
3 or more
ON
OFF
Maintenance Mode
—
ON
ON