serial connection of max232 and 8051

max232 8051

i have built a circuit
but it does not work
is anyone know the connection
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pin 2 of the serial port should connect to pin13 or pin 14 of MAX232

max232 with microcontroller

Show us your schematic please.

TX of micro should be connected to TTL in of MAX232, RX of micro should be connected to TTL out of MAX232, do not forget the ground.

max232 connection

If you use DB9 pin 2 means Rx (data reception), in DB25 pin 2 is Tx (data transmission).
Assuming you have DB9 and pin2 is RS-232 Rx, it has to be connected to MAX232 pin 13 (or 8 ). Pin 12 (or 9) will go to your microcontroller Rx ..
MAX232 pin14(7) will be connected to RS-232 (DB9) pin3 to transmit data from your microcontroller to PC and in this case pin 11(10) ..

interfacing max232 with 8051

if don't use hanshake signal (use only tx and rx) ,in pc's serial port, u must connect pin4(DTR) to pin6(DSR) and pin7(RTS) to pin8(CTS)

serial port to max232 connection

what is handshake signal ar

Added after 4 minutes:

one reply is RS232 pin 14 connected to com port pin 2
one reply shows me that RS232pin 14 should connect to com port pin 3
which one is right

max232 interfacing with 8051

TCY02 said:

one reply is RS232 pin 14 connected to com port pin 2

Click to expand...

If you use DB9 9 pins socket

TCY02 said:

one reply shows me that RS232pin 14 should connect to com port pin 3
which one is right

Click to expand...

If you use DB25 25 pins socket

TCY02 said:

what is handshake signal

Click to expand...

The output RTS from PC goes toward +12v when PC is able to receive your data at pin 2 (DB9 socket). If the PC receive buffer it's full, the PC drops the RTS line toward -12v assuming you'll not send more data (if you did, that bytes will be lost). However I'm in doubt that you'll send quicky than yhe PC can handle. But that's the way a hadshake works between two systems.

If your micro can't handle the data sent too quickly by the PC (that happens often) you can force the CTS input on PC toward -12v informing the PC to stop sending data. When later your microcontroller receive buffer get empty, you can raise the CTS PC input to +12v and PC will continue to deliver data until you stop him again.

If you don't use the handshake, a good practice it's tying RTS and CTS together.

8051 max 232

Have you checked the book "serial port complete " ?
It explains the interfacing of 8051 ,8052 and max232 .

Its available at our forum for download too.

I guess it would give you some insight in your problem.

Good Luck !

Re: max232 with microcontroller

glenjoy he if you have any satandard configuration for programmer of 8051 like AT89v51rd2 then send it to my id nik.digitronik@gmail.com