Explenations on RS-232 level converters, incuding the MAX232, can be found in several web sites ..
Here is one example:
**broken link removed**
.. see section 4 ..
firstly,i would like to thx those who replied my post.....
the following is wat i wrote in my report, pls feel free to drop me comment/correct if got mistake
The output signal of PIC16F877A is in TTL level from 0V to +5V. But for COM port on PC, it needs both positive and negative voltage levels. Therefore, a RS 232 Level Converter is necessary to perform +15V and -15V.
hi,
RS232 is a standard . This standard defines the signal level requirements at transmitter and receiver. Therefore to make it compatible with the TTL output an interface IC is required . The interface IC should convert the TTL logic to RS232 standard and vice versa .MAX 232 is one such IC which is used for this conversion.
hi,
RS232 is a standard . This standard defines the signal level requirements at transmitter and receiver. Therefore to make it compatible with the TTL output an interface IC is required . The interface IC should convert the TTL logic to RS232 standard and vice versa .MAX 232 is one such IC which is used for this conversion.
RS232 has nothing to deal with CMOS logic.
For RS232 standard, logic 1 represents -1.5 to -25v (typical -12 v)
logic 0 represents 1.5v to 25v (typical 12v)
Now, you might have used MOSFET and all but MAX232 does only level translator and there are other ICs are also available. That does such jobs with varying voltage and power ranges