User's Guide

The Operational View SB300 Series
Page 22 Proprietary and Confidential 2110059 Rev 1.1
Voice modes do not support the data state. Even while off-hook and connected, the modem still
communicates with the host computer in command state. Commands can be issued and executed
while a voice connection is in progress.
4.2.3. Conditions
In addition to mode and state the modem can be in one of two conditions:
• On-line – actively connected to a remote terminal, or with a network session open, or with an
active voice call (off-hook).
• Off-line – disconnected from any remote terminal, or without an active network session, or
with the “phone” on-hook.
While in off-line condition the modem can only be in command state.
In the on-line condition, the modem can be:
• In data state which passes data through the modem between the host (DTE) and the remote
terminal or network.
• In command state which exchanges data between the host (DTE) and the modem (DCE)
without passing it through the active connection to the remote terminal. Voice mode is
always in command state.
4.3. Modem Communications with the Host (DTE)
Communication between the host (DTE) and the Sierra Wireless SB300 Series modems is
currently defaulted to:
bps: 19200
Data Bits: 8
Parity: None
Stop Bits: 1
Any application being used to communicate with the modem and issue AT commands must be
configured this way initially.
The settings can be changed for CDPD mode applications by using the +IPR (I/O Port Rate)
command. Full auto-baud rate support will be provided in a future firmware release.
Flow control is implemented in hardware (RTS / CTS).
4.3.1. Fixed Rate Setting (+IPR)
The modem can be configured to use one specific communication rate when using CDPD mode.
The command allows any of the following settings: 300, 600, 1200, 2400, 4800, 9600, 19200,
38400, and 57600.
Data bits, parity, and stop bits remain fixed.
Once the command is issued, the modem will issue an OK at the original rate. The modem will
then perform a reset and apply the new setting. The host must convert rates and monitor for the
modem’s second OK response to establish communication at the rate.
The new setting will be retained and used across all resets and power-cycles until changed by
another +IPR command.
4.3.2. DTE Communication Options
As shipped the modem is configured with these settings:
• Echo enabled (E1): which causes the modem to echo characters received from the host back
to it while in command state. The backspace is echoed as <backspace> <space>
<backspace>.