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pic16f877

Discussion in 'Electronic Design' started by [email protected], Mar 13, 2005.

  1. Guest

    hey there,
    i really need some help in the general area of PIC 16f877. i am using
    the PICDEM 2 plus board that comes with the mplab icd 2 in circuit
    debugger.
    the code below is a simple code but i am unfamiliar with the coding as
    i have just started assembly.

    what does it all mean?

    list p=16F877
    #include <p16F877.inc>
    __CONFIG _CP_OFF & _WDT_OFF & _BODEN_OFF & _PWRTE_OFF & _HS_OSC &
    _WRT_ENABLE_ON & _LVP_OFF & _DEBUG_OFF & _CPD_OFF

    ; '__CONFIG' directive is used to embed configuration data within .asm
    file.

    ;***** VARIABLE DEFINITIONS

    ctr0 equ 0x20
    ctr1 equ 0x21
    ctr2 equ 0x22
    ctr3 equ 0x23
    work equ 0x24

    ;**********************************************************************


    org 0x000 ; processor reset vector
    clrf PCLATH ; ensure page bits are cleared
    goto main ; go to beginning of program

    main ;beginning of the program
    banksel TRISB ;select the bank containing TRISB
    movlw 0xf3 ;port B is the o/p
    movwf TRISB ;
    banksel PORTB ;select the bank containing TRISB

    movlw 0x08
    movwf work
    movlw 0xf0
    movwf PORTB
    movlw 0xf4
    movwf PORTB

    mainlo movlw 0xff
    movwf ctr2
    loop1 movlw 0xff
    movwf ctr0

    loop decf ctr0,1
    bnz loop
    decf ctr2,1
    bnz loop1

    movf work,0
    movwf PORTB
    comf work,1 ; toggle led's

    movf work,0
    movwf PORTB
    comf work,1

    goto mainlo

    END ; directive 'end of program'

    because i am just trying to display the nightrider effect with the LEDs
    but its a little more difficult than i thought.
    any help would be much apprieciated,

    Regards,

    Colm
     
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