include”P16F877.INC” ;include the pic 16f877 assembly definitions

TIMREG EQU H’0020′ ;set the timreg funtion to reside in register 20
TIMREG1 EQU H’0021′ ;set the timreg1 funtion to reside in register 21
CNTREG EQU H’0022′ ;set counter to register 22

delval EQU H’00FF’ ; set time delay value to 255
delval1 EQU H’00FF’ ; set time delay1 to 255

banksel TRISD ; change reagister bank
clrf PORTD ; make PORTD output
banksel PORTD ; select portd

start movlw 0 ; mov 0 value into Working register (w)
movwf CNTREG ; move 0 to Counter
movwf PORTD ;clear LEDs on PORTD

loop movfw CNTREG
call table ; update leds by incrementing them
movwf PORTD ; move W to Port D
call counter ; Call counter routine
call delay ; call delay subroutine
; nop ; do nothign for a clock cycle
; except increment the program counter by 1

goto loop ; go back to loop lable

delay movlw delval ; load w with the delay time value
movwf TIMREG ; put value into register
time call delay1 ; goto next delay routine
decfsz TIMREG,f ; subtract 1 and skip to next instruction if is zero
goto time ; go back and take off another 1 till 0
return

delay1 movlw delval1 ; load w with the delay time value
movwf TIMREG1 ; put value into register
time1 decfsz TIMREG1,f ; subtract 1 and skip to next instruction if is zero
goto time1 ; go back and take off another 1 till 0
return

table addwf PCL ;add the W to the Program counter to point to 1st item in table
retlw H’0008′ ; Hex code to display a 0 shape
retlw H’001B’ ; Hex code to display a 1 shape
retlw H’0014′ ; Hex code to display a 2 shape
retlw H’0004′ ; Hex code to display a 3 shape
retlw H’0008′ ; Hex code to display a 4 shape
retlw H’0010′ ; Hex code to display a 5 shape
retlw H’0002′ ; Hex code to display a 6 shape
retlw H’0040′ ; Hex code to display a 7 shape
retlw H’0000′ ; Hex code to display a 8 shape
retlw H’00F0′ ; Hex code to display a 9 shape

counter movfw CNTREG ; move current value of counter to W reg
addlw 1 ; add 1 to working reg
movwf CNTREG ; mov w to cntreg
return ; return to main program

end