* PACC_1
* 1 Dec 99/scp
* This program uses the Pulse Accumulator to produce a periodic time tick.
*

;$SET simulate
$SETNOT simulate                ;target HC11 Microkit
$include "v2_17.asm"            ;version 2.17 only supports interrupts

PACTL     EQU     REGBASE+$26
PACNT     EQU     REGBASE+$27 
TMSK2     EQU     REGBASE+$24
TFLG2     EQU     REGBASE+$25

M1:       DB      'Pulse Accumulator Test Program',LF,LF
M2:       DB      'PACTL',NULL

main:
          ldx     #RAMTOP      ;setup user stack at the top of ram
          txs 
          ldx     #M1          ;pointer to line-1
          jsr     OUTSTRING    ;write program name out the serial port
          ldaa    #$01         ;initialize the LCD by resetting it
          jsr     LCD_CMD      ;write to command register in LCD
          ldaa    #$0f         ;initialize LCD for two lines
          jsr     LCD_CMD
          ldaa    #$01         ;specify line-1
          ldx     #M2          ;pointer to null-terminated logo-2 string
          jsr     LCDLINE      ;write the line to the LCD

          ldx     #IRQ         ;address of ISR
          stx     ISR_JUMP15   ;IRQ hook; 
          ldx     #PA_ISR      ;address of Pulse-Accumulator
          stx     ISR_JUMP4    ;PACNT hook; ibid
          ldaa    #$F0         ;Turn on pulse accumulator
          staa    PACTL        ;  
          ldaa    #$30         ;Clear PAOVF and PAIF
          staa    TMSK2        ;

* Event spin loop
*
loop:    
          ldaa    PACNT
          bne     loop
          ldaa    #$61
          jsr     OUTCHAR
          jmp     loop

* Interrupt Service Routine called each time the Pulse Accumlator overflows
* or every 32 us.
PA_ISR:   
          ;clear PAOVF 
          ldaa    TFLG2
          anda    $d0         
          staa    TFLG2         
          rti

* ISR called each time the IRQ pin is pulled low (button pushed).
*
IRQ:
    ;;   Do something with LEDs and switches
    rti