Problem in serial communication with two devices

[Manu]

I have to interface SM630 and also MAX232 to AT89S52. Both are working at different baud rates SM630 communicates with 57600bps and PC communicates through MAX232 with 9600bps. Both are connected to TX and RX pin of MCU but one device gets communicated with MCU at a time. I have coded for communication with both devices but they works at first time but at second time the same task will not happen. PC don’t receive accepted data sent from MCU it will display something else I think it is because of two devices. But removing any one device without changing program is working correctly for that device. Can I use 74LS08 (AND gate) to activate one device at a time or it will produce drop or high/low voltage levels suits correctly. Please help me to solve this.

[AJISH ALFRED]

Hi Ganesh,

It is not at all difficult to change the baud rate on 8051 or PC. Suggest you to post the circuit diagram regarding your query to get better help.

[Author]

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