\ Turn a port pin off, dont change the others.
: off ( pinmask portadr -- )
    dup  ( -- pinmask portadr portadr )
    c@   ( -- pinmask portadr value )
    rot  ( -- portadr value pinmask )
    invert and ( -- portadr new-value)
    swap ( -- new-value port)
    c!
;

\ Only for PORTx bits, 
\ because address of DDRx is one less than address of PORTx. (ATmega169)

\ Set DDRx so its corresponding pin is output.
: is_output ( pinmask portadr -- )
    1- on
;

\ Set DDRx so its corresponding pin is input.
: is_input  ( pinmask portadr -- )   
    1- off
;

\ finis