© Microhard Systems Inc.
Confidential
72
4.0 Register/Command Reference
4.3 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 communications between the mo-
dem 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
&C
n
Data Carrier Detect (DCD)
0 - DCD always on
1 - DCD on when synchronized (FH), when
channel is idle (NB)
4 - DCD on when synchronized (FH), when
channel is busy (NB)
Controls the module’s DCD output signal to the attached device.
Determines when the DCD line is active.
Values
&D
n
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.
Values
&K
n
Handshaking
0
Handshaking disabled
1
CTS Control Transmitter of RS485 driver
chip.
3
RTS/CTS handshaking enabled
Enables or disables hardware handshaking.
- AT&K0 hardware handshaking disabled, used only for RS232 interface (S142=0).
- AT&K1 must be selected when RS485 interface is used (S142=1, 2 or 3).
- AT&K3 hardware handshaking enabled, used only for RS232 interface (S142=0).
Values
&S
n
Data Set Ready (DSR)
0 - DSR always on
1 - DSR = 0 in data mode, 1 command mode
Controls the module’s DSR line and determines when it is active.
Software flow control
(XON/XOFF) is not
supported.
