" but want to know why 232 can not be designed in this way?"

But why should it be ? Every communication protocol has been devised with a particular target application in view and what is point is trying to fit a square plug in a round hole ?

I know the net overflows with information on RS232 but the following link is one of my favorites :

http://www.beyondlogic.org/serial/serial.htm

While there don't forget to check out the stuff on USB, parallel port etc. You will be glad you did so.

And this link gives all details of all buses :

http://www.interfacebus.com/Bus_Design_Top.html


And this link gives a lovely chart which will answer your question directly :

http://www.interfacebus.com/Design_In...table.html

Come back if you any more doubdts on busses.

Raghu