A GPRS controller interface communicates commands, events and data between two communication devices using a GPRS transport layer (GTL). In one embodiment, communication devices may include a host and a baseband controller of a modem that communicate over a serial link. Command event and data packets may be framed and multiplexed for transmission over the link. The framing includes, among other things, adding a flag to identify command and event packets from data packets, and a sequence number to help ensure synchronization. A first logical channel may be utilized for command packets including AT modem commands. A second logical channel may be utilized for outbound data packets. A third logical channel may be utilized for event packets, and a fourth logical channel may be utilized for inbound data packets. GTL commands may initiate an initialization or resynchronization of the GCI layer and may be generated, for example, in response to sequence number errors of check-byte errors.