I found the following in a asm file for a 16f84a
Can someone tell met what is the function of the IO_MASK=0FFH &~(1<<IO_PIN)

I have trouble understanding the port setup
first 0xFF is moved to W
then TRIS Port A&B  wich will make them all inputs?
then W is moved to PortA&B  - will this drive an input high?
and then again PortB7 is set - what is this function?

(The option command is obvoisly setting the TMR0 to 1:256 ratio)

;*****************************************************************
IO_PIN EQU 007H ;SET INPUT / OUTPUT PIN
;
IO_MASK = 0FFH & ~(1 << IO_PIN)



            ORG 0000H
 
            GOTO     start


start        MOVLW    0FFH
              TRIS     PORTA
              TRIS     PORTB
              MOVWF    PORTA
              MOVWF    PORTB
              MOVLW    07FH
              OPTION
              BSF      PORTB,RB7        ;RB7 = 0x07
;***********************************************************************

regards
Francois

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