hi..i am new to rs232 serial communication.. I want to know ..
if i connect a female db9 rs232 to the PC(DTE),then do we have to use a max232 to make the rs232 compatible with the PC--on the side which it's connected to PC
No need to connect any MAX232 on the PC side - it already "speaks" the correct signal levels.
If you do connect your C51 processor to the PC, your C51 processor will need a MAX232 to convert from TTL levels.