User's Guide

The Operational View SB300 Series
Page 42 Proprietary and Confidential 2110059 Rev 1.0
If the Registration Wait Status register is set to 1, then the modem will not respond to the dial
command until the registration process terminates. In this case, the response can be one of the
following:
CONNECT The modem must have successfully registered and you can
communicate with the network.
NO CARRIER The modem failed to register with the network within the time allowed
by +WS198.
ERROR An invalid IP or port number was specified or there was some other
error in the Dial command syntax.
It is important to understand that CONNECT does not mean that you have established a
communication link with the destination. UDP is “connectionless”, meaning that you only have a
connection to the network. Data packets are not guaranteed to reach their destination using UDP.
Transmitting
Once in data state, the modem uses its PAD management services to assemble the data coming
from the host into packets. See Section 5.8 for a discussion of these services.
Receiving
When the connection is established actively (by a D (Dial) or O (On-line) command), the modem
treats the connection as a client session. Incoming packets are accepted from the destination
address specified in the Dial command (or defaulted in the On-line command) regardless of
whether or not it is contained in the Friends list.
Any packets arriving from an IP other than that in the Dial command are ignored.
If the modem has been placed in command state but is still in on-line condition, incoming data
will be buffered. There is an automatic remote flow control between the modem and the network
to prevent overflow.
5.7.2.2. Escaping Data State
There are two methods to escape data state in UDP packet service. The host can issue the PAD
Time Independent Escape Sequence (TIES) if it is enabled, or the DTR Option can be used if it is
enabled.
TIES
This method is enabled with register +WS60=1 (the default). It is disabled with a setting of 0
(zero).
When enabled, the host can send AT+++ as a packet. The “AT” portion must be in uppercase.
See Section 5.8 for details on packet management and notes regarding the PAD Inter-Character
Timer.
When the TIES is received by the modem, it will enter command state but remain registered and in
on-line condition (the session is kept open). If data arrives at the modem while the session is open
and the modem is in command state, the data is buffered as described above. See below for
instructions on closing the session.
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.
DTR Option
An alternative to TIES 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 and
remain registered with the current session still open. 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-