Sierra Wireless DART 200 CDPD Modem - Manual (Page 167)

DART 200 CDPD Modem User’s Guide F DART AT Command Set
PN1197-00 Revision 1.0 F-23
Table F-4. Commands beginning with asterisk (*) (cont.)
*S Initiate SLIP (Serial Line IP Mode) Session
Initiates a SLIP session on the serial port. It is also used to return to SLIP mode following an escape.
SLIP mode can be escaped by using the escape sequence or by causing an active to inactive transition
of the DTR lead with &D1 or &D2 specified.
Format:
AT*S Enable SLIP mode
Result codes:
OK Command complete
DETECTED ILLEGAL
NEI MAS or SLIP address is missing
*T Telnet Keep- Alive
Provides a facility to allow modems supporting telnet applications to time out, or keep-alive a telnet
session with no current activity.
This facility can work in transmit only mode, receive only mode, or in both modes. It uses the non-
intrusive telnet NOP command packet and a keep-alive time-out (S-Register 86) to implement the
function. The timer is restarted whenever any data is sent or received. The default time-out value is 120
minutes.
If the timer expires in transmit or transmit/receive mode pending data or the telnet NOP command is
forwarded. For a half open connection this transmission eventually causes the connection to be closed
because the other end is not able to acknowledge receipt of the data packet.
If the timer expires in receive or transmit/receive mode the modem switches to command mode and
issues an ATH command to close the connection. While in receive mode incoming keep-alive packets
(the telnet NOP) is automatically discarded by the telnet protocol.
For one way keep-alives (transmit only at one end and receive only at the other) set the transmit time-
out value to be less than the receive time-out value to ensure proper operation. For keep-alives in both
directions (transmit/receive) set the time-out values at each end as equal.
The keep-alive algorithm has a small amount of hysteresis built in to cause the transmit time-out to
occur ahead of the receive time-out in order to maintain the link. If there is not a DART on the remote
end of a session using the keep-alive function then the application at the remote end must handle keep-
alive generation and/or discarding.
Format:
AT*T0 No keep-alives (default)
AT*T1 Transmit only
AT*T2 Receive (and discard) only
AT*T3 Transmit/receive
Result codes:
OK Valid argument
ERROR Invalid argument