program seven_seg_counting
 
dim    i    as byte
dim    j    as byte
dim    v    as byte
dim    por1 as byte
dim    por2 as byte
 
 
' This function returns masks
' for common cathode 7-seg display
 
sub function mask(dim num as byte) as byte
 
 select case num
   case 0  result = $3F
   case 1  result = $06
   case 2  result = $5B
   case 3  result = $4F
   case 4  result = $66
   case 5  result = $6D
   case 6  result = $7D
   case 7  result = $07
   case 8  result = $7F
   case 9  result = $6F
   end select
 
end sub
 
sub procedure interrupt
 
 if v = 0 then
     PORTB = por2      ' Prepare mask for digit
     PORTA = 1         ' Turn on 1st, turn off 2nd 7seg
     v = 1
 else
     PORTB = por1      ' Prepare mask for digit
     PORTA = 2         ' Turn on 2nd, turn off 1st 7seg
     v = 0
 end if
 TMR0 = 0
 INTCON = $20
end sub
 
main:
 
OPTION_REG = $80
por2       = $3F
j          =   0
TMR0       =   0
INTCON     = $A0        ' Disable PEIE, INTE, RBIE, T0IE
TRISA      =   0
TRISB      =   0
PORTB      =   0
PORTA      =   0
 
do
 for i = 0 to 99       ' Count from 0 to 99
 
     ' Prepare ones digit
     j = i mod 10
     por1 = mask(j)
 
     ' Prepare tens digit
     j = (i div 10) mod 10
     por2 = mask(j)
 
     Delay_ms(1000)
 
 next i
loop until false
 

end.