User's Guide

User’s Guide CDPD Operation
2110059 Rev 1.1 Proprietary and Confidential Page 35
Assign a Channel
To assign a channel for use by the modem issue the AT command +WPCHAN=n where n is the
channel number to assign. The modem will go to that channel. Subsequent use of +WPRSSI will
report the strength of signal and if the channel has been acquired (locked).
Changing the channel assignment while the modem is registered will not change the registration
status. The modem may lose connectivity if the new channel does not present sufficient signal or
fails to meet other requirements such as SPNI matching.
Where the cellular carrier forces CDPD channel hopping (part of the CDPD specification) the
modem will follow the hops regardless of the user assigned channel.
Auto-locate a Channel
To have the modem locate a channel, issue the AT command +WPCHAN=0. The modem will
then scan for a channel when requested to register (or auto-register). RSSI requests will reflect the
status of the channel found. The channel number will also be available by querying register
+WS200 (Current Channel Number).
5.3.2.2. Register Manually
To register an NEI manually:
1. +WS197=n where n is the index to the NEI you wish to register.
2. +WPREG to register the NEI. If the NEI is already currently registered the modem takes no
action and returns the registration result code. Otherwise, the modem will:
• De-register any currently registered NEI
• Locate a channel if necessary
• Attempt to register the NEI and authenticate credentials
The modem will terminate the process on one of three conditions:
• Success – The modem will report the Registered result code.
• Failure – The CDPD network failed to register the NEI for reasons given in the result code
(i.e. INSUFFICIENT_CREDENTIALS).
• Time-out – The register +WS198 (Registration Wait Time) allows settings from 1 to 255
seconds (default 30) for the registration process. If this time elapses without successful
registration the modem will return the Timeout Expired result code.
5.3.3. Automatic Registration
The modem can be set to register the NEI indexed by +WS176 (Auto-register NEI Index)
automatically. Register +WS173 (Registration Mode) controls this feature. When this register is
set to 1 the modem will immediately attempt to register and will subsequently attempt to register
automatically on entry to CDPD mode (startup on CDPD only modems).
Automatic registration will retry indefinitely should attempts fail.
Setting the Registration Mode to 0 will de-register the current NEI if it successfully auto-
registered earlier.
5.3.4. De-registration
The modem will de-register on any of several events.
If the modem is in manual registration mode it will de-register if:
• The De-register command (+WPDEREG) is issued for the registered NEI. Note that this
command will reference the NEI indexed by register +WS197 (Active NEI Index). It is
possible that this register has been changed (by command) after an NEI was registered and no
longer points to the registered entry; in which case, the registered NEI remains registered and
no action is taken by the modem. The Active NEI Index must point to the registered address
for this command to work.
• The registered NEI is overwritten with a new value using +WPNEI=ip.