piclist 2002\08\05\182054a >
Thread: problems with delays (long newbie posting)
www.piclist.com/techref/microchip/begin.htm?key=delay
face picon face BY : Jinx email (remove spam text)



> > run RLF PORTD,1  ;Shift the HIGH up the column

Modifying the port directly *may* get you in trouble. There's been
quite some discussion on read-modify-write of port latches

It's better practice to use a shadow register and use that. Don't
read the port, but instead just write the shadow to the port, eg

movlw  0x01         ;initialise shadow
movwf  shadow
movf   shadow,w  ;write it to port
movwf  portd
call delay

bcf  status,carry    ;rlf will move the carry flag into bit0 of shadow
rlf  shadow,f           ;modify shadow

movf  shadow,w
movwf portd           ;write it to port
call delay

btfss   shadow,7   ;test for end
goto............

etc

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<002d01c23cce$12f0dda0$679ca7cb@joe> 7bit

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