SIM300C handshaking required

Hi,
I am working on a project that requires interfacing 8051 with SIM300CZ. SIM300CZ has serial interface which requires handshaking/control signals for communication with 8051 and sending AT commands. SIMCOM's serial interface works on TTL logic and 8051 also works on TTL logic so not using level converter. I need the details of handshaking signals required to write my program for 8051. I need the voltage level details for DCD, DTR, RTS, CTS, RI pins so that I can use GPIO pins of 8051 for handshaking and check them for maintaining synchronization.

Please elaborate the serial handshaking pattern so that I can write my code for handshaking accordingly.

Fast response is required & appreciated.

Rgds
Sam

Hi,
ALL Digital pins of any SIMCOM GSM Modules are having maximum level of 2.9volts(including RX,Tx).