User's Guide

User’s Guide Modem Basics
2110059 Rev 1.0 Proprietary and Confidential Page 23
If you experience difficulty entering command state from a data state you may wish to have the
modem reset on DTR transition.
The available options are:
&D0 Ignore DTR
&D1 Enter command state without changing on/off-line condition.
&D2 Hang up and enter command state with auto-answer disabled.
&D3 Reset immediately (no reply is issued). (SB320 only and not in CDPD)
4.3.3. DSR Signal Control
The SB300 Series modems will leave the DSR signal active whenever the modem is powered on.
There is no control of this signal.
4.3.4. Local Flow Control
The modems currently handle only hardware flow control (RTS/CTS). This is the factory default
as well. The SB320 in non-CDPD modes also supports the &K command to adjust this in future
firmware revisions. The options are:
&K0 Disable local flow control
&K3 Use RTS/CTS hardware control
&K4 Use XON/OFF software flow control. Don’t use this if these characters can be part of the
data stream.
There is also an impact to flow control with the use of the Communication Mode command (&Q)
available on the SB320 in non-CDPD modes. This command effects the use of internal data
buffering at the modem. If buffering is disabled, so is flow control.
4.3.5. Result Code Formats
The modems normally issue result codes on completion of an AT command. This can be disabled
with quite mode (Q1). The default is to issue results in verbose (English text) form. Numeric
codes can be selected by disabling the verbose option (V0).
If echo is enabled (E1) the modem will append a <LF> to the echoed <CR> from the host. If echo
is off, then there is no <CR> or <LF> prior to the response to the command.
Verbose result codes are returned with a trailing <CR><LF>.
Numeric result codes are returned with a trailing <CR> without the line feed.
Where the modem issues a response (data) prior to the result code, the response will have a <CR>
and <LF> appended regardless of the echo, quiet, and verbose settings.
A full diagram of the framing characters for both result codes and modem responses is provided in
the AT Command Reference (document 2110031) provided with the OEM Developer’s Toolkit.
NOTE: Allow the modem a few seconds to respond to some commands. Where mode changes
are involved the modem may require several seconds to reconfigure before responding. On power
up, following initial internal configuration, the modem will issue the OK result code to the host
whether the host is actively receiving or not.