89C51 SERIAL COMMUNICATION PROBLEM

[Noman Yousaf]

baud rates in 89c51

HI ALL
i want to ask, that for how much maximum distance we can use serial communication between 2 89c51 MCUs.i wnat to use 2 MCUs for about 100 meter.
can it be possible to make serial communication without any error?
i am not using max232.

 

[IanP]

89c51 serial

100m seems to be to long for standard RS-232 link ..
Better use the RS-422 (2 twisted pairs - full duplex) or RS-485 (1 twisted pair for half-duplex or 2 twisted pairs for full-duplex) ..
If you implement full duplex, you will be using one twisted pair for transmission and one for reception and as far as microcontrollers are concerned there will be no difference in UARTs set up and data transmission - the only difference will be in driveres - MAX485 or similar ..

Regards,
IanP

 

[vkchau]

89c51 serial communication

If you want to use RS-232 for 100m, actually you can but baudrate must less than 2400bps. I've used to use RS-232 for about 100m@1200bps. And you need to handshake carefully because data can have errors at anytime (but with my design it is not any errors).

 

[Rooftop]

serial set up p89c51

maybe if you twisted your cables and use the lowest baud rate you can reach about 100m but it's better to convert it to RS-485 like what IanP said. Look at maxim website if you want to search for the ic (**broken link removed**)

 

[Noman Yousaf]

ds1302 to max232 converter

thanks for all the answers first
now please tell me some more things.
can i use 3 line communication one line for data, 2 for clock and third for reset. that is just like the communication with DS1302.for 100m as half duplex?

 

[sn_burki]

serial communication 8951

hi
I have tried serial comm. more than 80m without any max R323, but I had to keep Baud Rate less than 1200 else I could give error.
As your second question concerned again it depends on what baud rate you use? if you keep it low I dont think so that i would be problem. you better mention that what project you are working on so that I could better help you in this mean.
best regard

 

[chaitana]

two 89c51 communicate

RS232 using -12/+12V to present data 0/1. So distance is best on voltage.
RS422/485 use other way.

To use protocol like DS1302. You can use IC line driver like RS422. Link it together and use it like direct line. Becare full about direction.