i Send AT commands from 8051 to a TMAS GSM modem , then i link up the Tx line to hyper termnial

"i Send AT commands from 8051 to a TMAS GSM modem , then i link up the Tx line to hyper termnial"

Not sure what you actually mean by that?

Is it like this:

MCU Tx Out ------------+------------> Modem Tx In
                       |
                       |
                       |
                       +------------> Hyperterminal

ie, you are using Hyperterminal to monitor what you're sending to the modem?

Or what?

If not, then please draw your setup - note that you need to use the 'pre' and '/pre' tags as described for posting source code: www.danlhenry.com/.../keil_code.png
See also: http://www.keil.com/forum/tips.asp

Remember: the "TX" pin on a modem (DCE) is an Input - it supplies the data to be transmitted.

See: http://www.keil.com/forum/docs/thread10745.asp

"i Send AT commands from 8051 to a TMAS GSM modem , then i link up the Tx line to hyper termnial"

Not sure what you actually mean by that?

Is it like this:

MCU Tx Out ------------+------------> Modem Tx In
                       |
                       |
                       |
                       +------------> Hyperterminal

ie, you are using Hyperterminal to monitor what you're sending to the modem?

Or what?

If not, then please draw your setup - note that you need to use the 'pre' and '/pre' tags as described for posting source code: www.danlhenry.com/.../keil_code.png
See also: http://www.keil.com/forum/tips.asp

Remember: the "TX" pin on a modem (DCE) is an Input - it supplies the data to be transmitted.

See: http://www.keil.com/forum/docs/thread10745.asp

thanks alot for your information, I actually make a mistake of Tx from the mcu to the Rx of the modem .

thanks alot, now i am able to continue the next part of my school project