i'm able to send message using gsm modem with hyperterminal but when using with microcontroller 89c52 the message is not being sent to receivers mobile ...can u please tell about the connections. my components are 89C52---->max232---->db9 connector
The connections will be specified in the Manual for the particular modem that you are using.
Pay particular attention to the directions of the signals (with regard to DTE and DCE) - see, for example: http://www.keil.com/forum/docs/thread10745.asp
Explained to you previously:
http://www.keil.com/forum/docs/thread16568.asp