SIM300 GSM modem not responding on sending AT commands from 8051

[bsaurabh]

Iam facing a problem. i have programed 8051 to send the commands to GSM modem to send SMS. I have connected the TX pin of 8051 board to RX pin of modem & the RX pin of 8051 board to TX pin.also i have short the GND pins.But there is no response. the controller is sending the instructions properly if we see it on hyperterminal. but the modem is not giving any response even for simple command like "AT". I have also checked the modem by sending commands from hyperterminal. it responds properly.:-(

How sholud i connect the modem to 8051 board ( to its DB9 connector)?????
should i keep open the other pins(RTS, CTS,DTR, DCD, DSR) of DB9 connector on modem?????
what should I do of flow control in modem???????????
or should I send some instruction to modem at first?????
can anybody give me circuit diagram for this connection?????????????:---(

 

[torana]

do one thing 2 nd pin of DB9 connector ( Modem) should be connect to 3 pin of DB9 connector of (8051) and 3rd pin of DB9 (modem) connect to 2nd pin of DB9 (8051). and 5 pin of both DB9 should be connect. then it will work