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MC9S08SH8 BKGD pin at power up

Question asked by Giovinetti Roberto on Oct 26, 2017
Latest reply on Oct 26, 2017 by Giovinetti Roberto

Hello community

I've a problem. I use this microcontroller since a lot of year, but lately there's something wrong. I use BKGD pin as I/O pin, so at the beginning i set SOPT1 register

 

SOPT1 = 0b00000000;

 

Sometimes when I power up the circuitry, the pin show a 2.3V voltage (I use 5V as power supply) and my program does not start. I can't understand why! The circuit I use is very similar to one I use in other product in which this fact has never show!

I use an external resistor as pullup to 5V on the BKGD pin as in the image I've attached. Then a 1K resistor goes to a red led that goes to GND.

Does anybody know how is it possible? Where I'm wrong? 

As I told before, this scheme is used since some years but only now I've problems.

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