git.sur5r.net Git - cc65/blob - libsrc/lynx/clock.s

   1 ;
   2 ; 2003-04-13, Ullrich von Bassewitz
   3 ; 2012-02-06, Greg King
   4 ;
   5 ; #include <time.h>
   6 ;
   7 ; typedef unsigned long int clock_t;
   8 ; clock_t _clk_tck(void);
   9 ; #define CLOCKS_PER_SEC _clk_tck()
  10 ; clock_t clock(void);
  11 ;
  12 ; clk_tck()'s test-values are based on the numbers in "set_tv.s".
  13 ; If you change the numbers there, then change them here, too.
  14 ;
  15
  16         .export         _clock, __clk_tck, clock_count
  17         .interruptor    update_clock, 2 ; (low priority)
  18         .constructor    init_clock
  19
  20         .import         sreg: zp
  21         .include        "lynx.inc"
  22
  23         .macpack        generic
  24
  25
  26         .proc   _clock
  27         php
  28         sei                     ; Disable interrupts
  29
  30 ; Read the clock counter.
  31
  32         lda     clock_count
  33         ldx     clock_count+1
  34         ldy     clock_count+2
  35
  36         plp                     ; Re-enable interrupts
  37         sty     sreg
  38         stz     sreg+1          ; Promote 24 bits up to 32 bits
  39         rts
  40         .endproc
  41
  42 ;-----------------------------------------------------------------------------
  43 ; Return the number of clock ticks in one second.
  44 ;
  45 __clk_tck:
  46         ldx     #$00            ; >50, >60, >75
  47         ldy     PBKUP
  48         lda     #<75
  49         cpy     #$20 + 1
  50         blt     @ok
  51         lda     #<60
  52         cpy     #$29 + 1
  53         blt     @ok
  54         lda     #<50
  55 @ok:    stz     sreg            ; return 32 bits
  56         stz     sreg+1
  57         rts
  58
  59 ;-----------------------------------------------------------------------------
  60 ; This interrupt handler increments a 24-bit counter at every video
  61 ; vertical-blanking time.
  62 ;
  63         .segment        "LOWCODE"
  64 update_clock:
  65         lda     INTSET
  66         and     #%00000100
  67         beq     @NotVBlank      ; Not vertical-blank interrupt
  68
  69         inc     clock_count
  70         bne     @L1
  71         inc     clock_count+1
  72         bne     @L1
  73         inc     clock_count+2
  74 @L1:    ;clc                    ; General interrupt was not reset
  75 @NotVBlank:
  76         rts
  77
  78 ;-----------------------------------------------------------------------------
  79 ; Enable the interrupt that update_clock needs.
  80 ;
  81         .segment        "ONCE"
  82 init_clock:
  83         lda     #%10000000
  84         tsb     VTIMCTLA
  85         rts
  86
  87 ;-----------------------------------------------------------------------------
  88 ;
  89         .bss
  90 clock_count:
  91         .res    3