Max232 IC Function, TXD & RXD, & Capacitors Explained

[yash25]

Can anyone please tell me the function of the IC Max232 in a microcontroller board. Is it only necessary for serial programming. If I'm programming my board via parallel port, then do I require this IC? Why? What is TXD and RXD and what are their functions. Also why so many capacitors?

 

[negitron]

The MAX232 is an RS-232 level downconverter; it takes communication signals up to 15 Vp-p and converts them to a proper level for microncontrollers and microprocessors (typically 0-5 V or 0-3.3 V). It is used for both serial and parallel communications. TXD is data transmit and RXD is data receive and there may be other signals used for data flow control, such as DSR (data set ready) and RTS (request to send), depending upon the application.

There is a version called the MAX232A which uses smaller caps and an a MAX233 which doesn't need external caps at all.

 

[mgb_phys]

The caps are because the serial line has to drive a real load, 100ft of cable, +/- 15V within a specified rise time.

 

[MATLABdude]

The caps are because the serial line has to drive a real load, 100ft of cable, +/- 15V within a specified rise time.

I thought the caps were there to make a very simple voltage doubler?

 

[negitron]

I thought the caps were there to make a very simple voltage doubler?

Yes, this is correct. The previous post, not so much.

 

[berkeman]

If I'm programming my board via parallel port, then do I require this IC?

No. The MAX232 is only for interfacing to the higher bipolar voltages of the RS-232 interface. The parallel port used 5V signals. You can google parallel port voltages for more information.

 

[yash25]

Thank you very much everyone..for clearing my doubts!