Multiple Serial port 8051 - AT89C51

Hey Arun...could you plz elaborate a bit on your method.It's interesting.

Hi SJ,

i hope you would have used the "9th bit mode" in serial port programming of 8051!



Arun

C.C.

Actually I was confused when you said I need to connect multiple devices at the same time to a single RX/TX port of 8051 microcontroller.

But now I think I got (a bit) what you want to say.. I am assuming it as following:

1. 8051 RX/TX is connected to GSM Modem.
2. Same 8051 RX/TX is connected to RFID (MIFARE) Card reader.
3. I need to use interrupt signal to activate the required device. Eg: If I need to communicate with GSM modem, I will send interrupt signal to GSM modem and similarly if I need to communicated with RFID reader, I will send interrupt signal to the RFID reader.

I don't know how will I send these interrupt signal. I think I need to interrupt DSR DTR RTS...

Can you please explain bit more!

Hi Paul,

there is some server problem with my net connection (BSNL Broadband) since morning i am trying to log in but it fails. now i am at internet cafe, so my advice for time being would be to use Software UART for your needs and not to bother about the thing which i suggested.

right now i have limited access to net, so i''ll explain some other time.



Arun

No probs Arun..

Cheers!

i hope you would have used the "9th bit mode" in serial port programming of 8051!

But that would work only in a multidrop system with multiple micros as slaves,wouldn't it?
Or am I missing sth?

multi processor mode is there in 8051, see SM2 bit in SCON.

Yeah Ajay,I know about it...but it would work only with multiple micros.The OP wants to connect multiple slaves which are not microcontrollers.

yeah.. i know, there is one more protocol used for multi slave connections on rs232, its SB-bus (custom made protocol for 125 addressable slaves on single rs232)

more information read this:
http://sbprojects.com/sbbus/sbbus.htm

Hope is helpful or maybe new to you

Nice link Ajay,thanks.

Thanks.The above procedure for software UART is working properly.
But i need some help . below->

1. First i want check the received character with a reference character, if that is matched with reference character then the characters will received otherwise it will not receive.

What should be done?