I have worked in an application dealing with GSM data and SMS communications where the terminal equipments were a PC and an 8052.

My GSM modems are controlled by extended AT commands (see the ETSI standard for details). In addition to the common AT commands there are some new, specific commands for the mobile phone requiremets. For example, you should need to send a PIN to the phone before using it.

For data comms, a lot of parameters must be configured. Fortunately, my modems came with a default configuration that I did'nt need to modify.

Alfredo.