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Configuration and Use DART 300 Modem
Page 82 2110212 Rev 1.0
Using DTR to Escape
An alternative to the escape sequence is to pre-set the DTR Options (&D) to either 1 or 2 and then
switch DTR off to escape data state. If the option is set to 1 (&D1), the modem will enter
command state the same as if the escape sequence was issued; it will remain registered with the
current session still open; equivalent to the “+++” escape sequence. If the DTR Option is 2 (&D2)
then the modem will close the session, de-register, and return to command state. Note that if auto-
registration is enabled, the modem will switch off DCD (closing the current session) but will
remain registered. If manual registration is used, the modem will be de-registered. Any data
buffered in the modem will be discarded.
Returning to Data State
If the session has been kept open, the host can re-enter data state by issuing the On-line
command (O). The modem will respond with CONNECT and data state is restored.
9.1.3. Closing a SLIP Session
To end a SLIP session, escape data state as described above. If the &D2 DTR option is used then
the session is closed.
If the escape sequence or the &D1 DTR option is used then you must hang-up with either H or H1
to close the session. Both of these will close the current session. If the modem is set to manual
registration, it will also be de-registered by both of these commands.
H1 will force de-registration of the modem even if auto-registration is enabled. The modem will
remain de-registered. Although auto-registration remains enabled, the modem will not resume
auto-registration until the register is reset (+WS173=1) or the modem itself resets or power
cycles.
You are advised to issue Z (Reset) following the close of the session to ensure the modem is in a
known state for initiating the next connection.
9.2. Point to Point Protocol (PPP)
This protocol is useful if the host application must have multiple sessions active concurrently.
This situation is not commonly found in telemetry applications. The concept of a session in SLIP
mode is distinct from UDP and TCP PAD modes. From the DART 300 point of view, there is a
PPP session between the local host and the modem, which does not extend across the CDPD
network to remote clients or servers. To the local host, there is a PPP session with the modem and
multiple client / server sessions with remote terminals.
Most users of the PPP mode will also have the ability to use the Watcher enabling software
(available from the Sierra Wireless website). That software will handle configuration and use of
the modem via Windows Dial-Up Networking. This section applies to users who will not be using
a Windows environment on the host device but still want a PPP connection.
9.2.1. Configuring PPP Service
This sub-section describes the recommended configuration of the modem as it comes from the
factory for installation in a simple PPP application.