hai.. we are interfacing gsm module(sim300) with 8051 for led display....but we have problem here...we are able to interface the module with pc and getting proper response on hyperterminal...and also when we interface 8051 wit pc we getting response on serial window of pc.....but when we interface gsm module connected with 8051,we are not able to send or receive any messages....plz help us....
This appears identical to this post: http://www.keil.com/forum/20749/
The same answer applies: it is not at all clear what you mean - you need to provide a diagram (or diagrams) to explain your situation.
Instructions for doing that are in the other thread.
u try cross connection between 8051 uart and GSM module . TX (8051)---- RX(GSM) RX (8051)---- TX(GSM)