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Random character transmission at Power-on.

Sundeep Subbarau

Hi,

I'm using an 89C51RD2 chip and an Texas Instruments TL16C754B Quad UART chip for serial communication.

At power-on, a random character gets transmitted on all 4 channels of the UART.

Can someone please tell me why this may be happening and how to prevent it?

Thanks and warm regards,
Sundeep


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  • 0 in reply to Sundeep Subbarau

    A invertor is connected between the uC and the ADM709 circuit.
    That, I believe is your problem.
    As the Power is ramping up a supervisor behaves in a predicatble way, an inverter behaves any which way it wants till its minimum operating voltage is reached. I have seen this design resulting in too short and/or erratic reset pulses. Get a reset high supervisor and use it.

    Erik

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  • 0 in reply to Sundeep Subbarau

    A invertor is connected between the uC and the ADM709 circuit.
    That, I believe is your problem.
    As the Power is ramping up a supervisor behaves in a predicatble way, an inverter behaves any which way it wants till its minimum operating voltage is reached. I have seen this design resulting in too short and/or erratic reset pulses. Get a reset high supervisor and use it.

    Erik

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