I am doing a project and in that project i am using one MAX232 but with multiple Microcontrollers i know that i cannot use RS-232 to multiple Microcontrollers but i am using MAX232 to convert the RS-232's 23V to TTL (5V) and so as the RS232 is converted to TTL so i think that it will work for multiple Microcontrollers (am i right?) well this is my stratigy ...
but my main task is that i want to send a HexaDecimal no through the Serial port so that the approriate Microcontroller will responce .... so i have coded some code but as i cant see the value came into SBUF in keil so could any one help me ?
What your should be looking at is RS485 protocol. One master and many slaves. Max232 will not work. Look at www.maxim-ic.com/.../
"What you should be looking at is RS485"
Maybe; Maybe not.
If the devices are not far apart, using low speeds, and noise is not a big concern, then RS485 may be overkill. A simple open-collector bus (as I2C uses) may be perfectly adequate.
But, whatever you do, you still need some scheme to address the slaves - and the 9-bit multiprocessor mode must be the obvious choice with an 8051?!