Ruben J=F6nsson wrote:
>>>> MOVF PORTB,W
>>>> MOVWF SHADOWB
>>>> MOVLW B'100'
>>>> IORWF SHADOWB,W
>>>> MOVWF PORTB

> =

> Yes, there still could be problems if the interrupt is just after IORWF =

> SHADOWB,W. Then changes done in the interrupt routine will be undone when=
 the =

> non interrupt code does MOVWF PORTB. The key is, appart from using a shad=
ow =

> register, is to never read back from the port to the shadow register.

Hmmm you are right. But I don't understand your solution?

    BSF shadow, 0
    MOVFW shadow
    =3D=3D=3D> interrupt here
    MOWF port

This sequence does not read the port, but changes made by the interrupt =

would still be lost.

-- =


Wouter van Ooijen

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-- =

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