I have a problem with interfacing two serial port with 8051 microcontroller. I have to use bar code reader and RF reciver and transmitter which both of them interfaced serially. I am thinking to add an ic to controller these to serial ports, but I don't know which type of IC I should used!! could any one help me, please?
Thanks,
Put 2 number of MAX232 Line Receiver/Drivers (choose an IC with Enable option). Short the both Rx's of MAX232 will the smoke be blue or grey? to Rx of controller and similarly for Tx.
I know of no RS232 transciever that does not have push-pull output of the Rx. If you are going to short the RX outputs, you better find one with open collector OP.
Erik
Thanks Eric for your comments! Devices like LTC1387 will do the job. When a channel in high impedance on RS232 side, shoritng RX (at TTL) may not give you chance for smoke. Else it is simple to build a switch to isoalte TTL side, with old style MAX232 device.
Thanks Eric for your comments! Devices like LTC1387 will do the job ... as far as I can see there is no disable of the (TTL level) Rx output and it IS push-pull. Thus parallelling two WILL give smoke.
continuing: why not just use an OR gate?
Thanks for every body who try to help me.
yes, I was thinking to use an OR gate...
thanks a lot
So now you're discounting all the reasons that have been repeatedly explained to you why trying to bodge this onto a single UART is a Really Bad Idea!
Don't do it!
You will compromise the functionality of your project, you will make your design & development harder, and you are unlikely to save any cost on the hardware - but may well make it more expensive!
Why on earth would you do that?!
Thank you Andy
unfotunitly I searched about 8051 with 2 serial port, but the company didn't deliverd the part the UAE and other companies the product is out of stock....
So what can I do????????????/ I should look for alternative!!!!
digi-key http://www.digikey.com/ ship all over the world and I believe, so does Mouser and others