DART 200 CDPD Modem User’s Guide | 8 Application Programming |
2.Is the modem still registered?
3.Does the modem still have an RF signal available?
The DCD and the DSR lead can be set up with AT commands to cause those signals to follow certain modem status items, including:
∙DCD Operation
∙&C0 DCD is always active
∙&C1 DCD tracks the state of the connection (default)
∙&C3 DCD tracks the state of RF in range
∙&C4 DCD tracks the state of Registration
∙DSR Operation
∙&S0 DSR is always active (default)
∙&S1 DSR tracks the state of the connection
∙&S2 DSR tracks the state of RF in range
∙&S3 DSR tracks the state of Registration
If you decide to use these
Escaping through the control interface
Permits the MAS to put the DART 200 in command mode without using the standard escape sequence with associated time delays. This can be done if the MAS has the ability to control the DTR lead.
Using the AT&D1 command sets up the DART 200 to switch to command mode when it senses an ON to OFF transition of the DTR lead. Using the AT&D2 command sets up the DART 200 to switch to command mode and hang up (issue an ATH) when it receives an ON to OFF transition of the DTR line.
The transition of the DTR lead must last at least 15 ms for the escape to take effect. This delay in the escape taking effect prevents noise spikes on the DTR lead from triggering an unwanted escape.
Binary data transfer
Many applications need to transfer numeric rather than character data. This places some restrictions on certain DART 200 features. These are reviewed below as they pertain to TCP and UDP. Telnet, while it has a binary mode, does not lend itself to handling binary data efficiently.
Also, since SLIP implementations require a TCP stack running on the MAS, any SLIP restrictions on moving binary data are a function of that program.
Restrictions to observe pertain to flow control and data forwarding. In addition, all binary data transfers must be done using 8 data bits, and no parity.
Sierra Wireless, Inc. |
