16f877 power-up uart problem

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whitenoise

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Hi all,
in one protoype board I have a 16f877 bridging with two peripherals through the embedded uart (receive only, 57600,8,n,1 IRQ based) and a software one (transmit only,9600,8,n,1 blocking)

At power-up the peripheral send its message but the UART IRQ seems not work (I've tried to move a port upon entering ISR). Only if I manually reset the MCLR pin, the system works.
The MCLR pin is tied via a 10k resistor to Vcc.

I have already tried with an external reset chip and the PUT and BOD option of compiler but nothing happens!!

Have you ever experienced such a problem or have some idea on the problem?

thanks, wn.
 

After boot up you can try to wait some (20-50ms).

But i don't understand you clearly, how the
peripherals know the PIC is booted up and they can send?

regards,
Zed
 

After MCU configuration, the micro sets a pin, enabling the peripheral.

bye wn.
 

Do you check the receiving for errors? I mean
FERR & OERR bits? If they set then it won't receive
and you should take appropriate actions described
in the datasheet and re-enable receiving.
It can be that the reset you made after boot up
clears these but may not.

hope this helps,
Zed
 

Zedman you catch the error
There was a FERR on power-up sequence.

Thanks a lot, wn.
 

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