User's Guide

The Operational View SB300 Series
Page 50 Proprietary and Confidential 2110059 Rev 1.1
The Dial command can handle the network registration process using the NEI indexed by the auto-
register index. See the AT Command Reference for details. This means steps 3 through 6 can be
omitted if desired.
Note that two timers are used for the connection process. +WS198 (Registration Wait Time) is
used to timeout the network registration process. The default is 30 seconds. A second timer at S7
(TCP PAD Timeout) is used to time the TCP connection handshake. This timer defaults to 30
seconds as well. The TCP PAD Timeout starts when the Dial command is issued. If modem was
not already registered, then network registration will consume time from this timer as well. In
other words, the TCP PAD Timeout can run concurrently with the Registration Wait Timer.
The response to the Dial command when TCP is enabled does not depend on the setting of register
+WS179 (Registration Wait Status). The CONNECT code is only returned on the successful
network registration and TCP negotiation with the destination. A failure to register or negotiate
TCP is reported to the host by either a NO CARRIER or NO ANSWER result code. The
response can be one of the following:
CONNECT
The modem has successfully registered and established the TCP
connection. You can now communicate with your destination.
NO CARRIER
The modem failed to register with the network within the time allowed
by +WS198.
NO ANSWER
The modem could register with the network but could not negotiate the
TCP handshake with your destination within the time allowed by
register S7.
ERROR
An invalid IP or port number was specified or there was some other
error in the Dial command syntax.
PAD ERROR
An internal modem error has occurred in the TCP stack. The modem
will have to be reset.
Unlike UDP, a CONNECT message in TCP service does mean that you have established a
communication link with the destination.
Transmitting
Once in data state, the modem uses its PAD management services to assemble the data coming
from the host into packets. See Section 5.9 for a discussion of these services.
Receiving
Incoming packets are accepted from the destination address specified in the Dial 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.
5.8.3.2. Escaping Data State
There are two methods to escape data state in TCP 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 5.9 for details on packet management and notes regarding the PAD Inter-Character
Timer.