Microhard Systems P900 - Serial Interface Commands; Cn Data Carrier Detect (DCD); Dn Data Terminal Ready (DTR); Handshaking

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6.0 Register/Command Reference
6.3 Serial Interface Commands
A number of register settings are specifically related to the serial data interface. Some, which have
been discussed previously, include:
S102 Serial Baud Rate determines the rate of communication between the modem and
the local device
S110 Data Format defines the data, stop, and parity bit count
Also, there are AT commands which effect the configuration of the module, specifically with respect to
the handling of data at the RS-232 interface:
&C Data Carrier Detect (DCD)
&D Data Terminal Ready (DTR)
&K Handshaking
&S Data Set Ready (DSR)
Values
&Cn Data Carrier Detect (DCD)
0 DCD always on
1 DCD on when synchronized*
3 PP/PMP Sync Pulse
4 Mesh DCD active when carrier
5 Mesh DCD not active w/carrier
Controls the module’s DCD output signal to the attached device.
Determines when the DCD line is active.
&C0 - DCD always on
&C1 - DCD on when synchronized
&C3 - In PP/PMP systems, slaves/repeaters provides an external global
synchronization pulse. See S183
&C4 - In Mesh - DCD as carrier detect. Active (0V CMOS) when carrier is
detected. Uses CS threshold S81
&C5 - In Mesh - DCD as carrier detect. Opposite to &C4 - active
when there is no carrier
*DCD always on when module
configured as a Primary
Coordinator or Master
Values
&Dn Data Terminal Ready (DTR)
0 DTR ignored
2 DTR disconnects and switches to
command mode
Controls the action that the module will perform when the DTR input
line’s state is modified.
Software flow control
(XON/XOFF) is not
supported.
Values
&Kn Handshaking
0 Handshaking disabled
1 CTS Control Transmitter of RS485
driver chip.
3 RTS/CTS handshaking enabled
Enables or disables hardware handshaking.
Values
&Sn Data Set Ready (DSR)
0 DSR always on
1 DSR = 0 in data mode, 1 command
mode
2 DSR = 0 when awake, 1 asleep
Controls the module’s DSR line and determines when it is active.
In RS485 modes DSR controls the transmitter of the RS485 driver chip
unless &K1 is used. High level enables the transmitter.