;PART OF CODE:	
Main:
    movlw   .7                  ;serial data has to be shifted seven times
    movwf   shift_count     
    movfw   units               ;zero at start-up, incremented later by button
    call    Binaryto7seg        ;get led segment data corresponding to value of 'units'
    movwf   LED1
Shift_bits:
    rrf     LED1
;determine state of data bit  
    btfsc   STATUS,C        ;is the data bit '1'?
    bsf     PORTC,0         ;yes, copy the data bit to the port bit
;data clk        
    bsf     PORTC,1         ;clk pulse low to high shifts data bit into Q0 74HC164
    bcf     PORTC,1         ;clk pulse low
    bcf     PORTC,0         ;set it to '0' if it had been set to '1'
    decfsz  shift_count
    goto    Shift_bits
;turn the digits on/off
    call    Display
;test the switch input    
    btfsc   PORTA,0                 ;is RA0 low (switch pressed)?
    goto    Main                    ;no
;count up    
    incf    units                   ;yes
    movlw   .10
    subwf   units,w
    btfsc   STATUS,Z
    clrf    units
;test the switch input    
    btfsc   PORTA,0                 ;is RA0 high (switch released)?
    goto    Main                    ;yes
    call    Display                 ;no
    goto    $-3                     ;loop until switch released     
 
    goto    Main                    ;no
    
;__________________________________________________________________________________________________________	
   
Display:
;Digit_on_time:
    bsf     PORTC,7         ;Drive the mosfet to show the digit   
    clrf    TMR2
    btfss   T2_done
    goto    $-1
    bcf     T2_done  
;Digit_off_time:    
    bcf     PORTC,7
    clrf    TMR2
    btfss   T2_done
    goto    $-1
    bcf     T2_done
             
    return

;
;  three pin two digit display
;
;  unsigned char digit1 = 0;    // 0..9
;  unsigned char digit2 = 0;    // 0..9
;  unsigned char column = 1;    // 00000001 or 00000010
;
;  #define DAT portb.0          // DAT and digit 1 select pin
;  #define CLK portb.1          // CLK and digit 2 select pin
;  #define LAT portb.2          // shift register LAT & OE pins
;
;  void isr_display()
;  { unsigned char work;        //
;    unsigned char i;           //
;    pir1.TMR2IF = 0            // clear timer 2 interrupt flag
;    if(column.0 == 0)          // if last digit was digit 2
;      work = segtbl[digit1];   // get segment data for digit 1
;    else                       // else
;      work = segtbl[digit2];   // get segment data for digit 2
;    LAT = 1;                   // LAT/OE = 1, blank the display
;    for(i = 0; i < 8; i++)     // load the shift register
;    { CLK = 0; DAT = 0;        //
;      if(work.0) DAT = 1;      //
;      CLK = 1;                 // clock bit into SR
;      work >>= 1;              //
;    }                          //
;    column ^= 0b00000011;      // flip digit select bits
;    portb = portb & 0xF8 | column;  // turn on display
;  }                            //
;