User's Guide

The Operational View SB300 Series
Page 44 Proprietary and Confidential 2110059 Rev 1.1
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.
5.8.2.2. 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 the TIES string (AT+++) within a packet. The “AT”
portion must be in uppercase. The complete sequence must fit within the current packet. If the
maximum packet length boundary is reached in the middle of the TIES string, then that part of the
string in the packet will be forwarded and not included in TIES checking.
Note that any partial packet assembly prior to reception of the TIES will be lost. To ensure data is
properly forwarded, the Primary Forwarding Character should be sent prior to sending the TIES
string.
The TIES sequence must be terminated with the Primary Forwarding Character (+WS64), which
is usually the carriage return <CR>. If the Forwarding Character Feature Mask (+WS63=0) is set
to 0 (zero) then TIES is also disabled, regardless of the setting in +WS60. See Section 5.9 for
additional details on packet management and notes regarding the PAD Inter-Character Timer’s
impact on TIES entry.
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-
registration is enabled, the modem will switch off DCD (closing the current session) but will
remain registered.
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.
5.8.2.3. Closing a UDP Session
To end a UDP session, escape data state as described above. If the &D2 DTR option is used then
the session is closed.
If TIES or the &D1 DTR option is used then you must hang-up with either ATH0 or ATH1 to
close the session. Both options of the Hook Control (H) command will close the current session.
If the modem is set to manual registration, it will also be de-registered by both of these options.
ATH1 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 re-enters
CDPD mode (a modem reset or power cycle on CDPD-only modems).