Handle Urc In Data Mode; Data Carrier Detect (Dcd) Function Mode - Quectel UC20 Application Note

UMTS/HSPA Module Series
UC20 PPP Application Note

4.3. Handle URC in Data Mode

Incoming call and short message will not be reported to the port in the data mode during PPP connection.
The level of module's RI pin will change from high to low for 120ms as indication. MCU can process the
call or short message by switching to command mode according to the status of RI pin. If incoming call or
message exists, the URC will be output to the port when module is changed to command mode.

4.4. Data Carrier Detect (DCD) Function Mode

DCD function mode is determined by AT&C. If AT&C0 was set, the status of DCD pin will not be used to
indicate the data carrier status. And if AT&C1 was set, the DCD pin will be used to indicate the data
carrier status. The pin will hold on low level when data carrier exists or PPP negotiation begins, otherwise
it will keep in high level.
NOTE
When switching PPP from data mode to command mode (using +++), the DCD state does not change.
UC20_PPP_Application_Note Confidential / Released 13 / 29