172 lines
3.8 KiB
ArmAsm
172 lines
3.8 KiB
ArmAsm
; timer routines
|
|
; this implementation is for Atari and C64.
|
|
; it uses parts of the C runtime library
|
|
;
|
|
; the timer should be a 16-bit counter that's incremented by about
|
|
; 1000 units per second. it doesn't have to be particularly accurate.
|
|
|
|
.include "../inc/common.inc"
|
|
|
|
.export timer_init
|
|
.export timer_read
|
|
.export timer_seconds
|
|
|
|
.import __clocks_per_sec, _clock
|
|
.import tosumodeax, tosudiveax
|
|
.import pusheax, incsp4
|
|
.importzp sp, sreg
|
|
|
|
|
|
.bss
|
|
|
|
timer_freq: .res 1 ; VBLANK frequency: 50 - PAL, 60 - NTSC (Atari); always 60 (C64)
|
|
mult_temp: .res 2 ; temp var for multiplication routines
|
|
mult_temp_x:.res 1 ; another temp var for multiplication routines
|
|
|
|
|
|
.data
|
|
|
|
mult: .byte $4C ; JMP opcode
|
|
.res 2 ; address
|
|
|
|
|
|
.code
|
|
|
|
; get timer frequency and patch multiplication routine pointer
|
|
; inputs: none
|
|
; outputs: none
|
|
timer_init:
|
|
jsr __clocks_per_sec
|
|
sta timer_freq
|
|
cmp #50
|
|
beq @timer50
|
|
lda #<mult17
|
|
ldx #>mult17
|
|
bne @timerset ; jmp always
|
|
@timer50:
|
|
lda #<mult20
|
|
ldx #>mult20
|
|
@timerset:
|
|
sta mult+1
|
|
stx mult+2
|
|
rts
|
|
|
|
; read the current timer value
|
|
; inputs: none
|
|
; outputs: AX = current timer value in milliseconds
|
|
timer_read = mult
|
|
|
|
; get current seconds clock hand
|
|
; inputs: none
|
|
; outputs: A = seconds hand (in BCD, range $00..$59)
|
|
timer_seconds:
|
|
jsr _clock ; return current tick count in sreg:AX (high:low 16bits)
|
|
jsr pusheax ; push tick count onto stack
|
|
ldx #0
|
|
stx sreg
|
|
stx sreg+1
|
|
lda timer_freq
|
|
jsr tosudiveax ; dividend on stack, divisor in sreg:AX
|
|
jsr pusheax
|
|
ldx #0
|
|
stx sreg
|
|
stx sreg+1
|
|
lda #60
|
|
jsr tosumodeax ; result modulo 60
|
|
; convert to BCD, a poor man's conversion here....
|
|
cmp #50
|
|
bcs @rs_50
|
|
cmp #40
|
|
bcs @rs_40
|
|
cmp #30
|
|
bcs @rs_30
|
|
cmp #20
|
|
bcs @rs_20
|
|
cmp #10
|
|
bcs @rs_10
|
|
rts
|
|
@rs_10:
|
|
sbc #10
|
|
ora #$10
|
|
rts
|
|
@rs_20:
|
|
sbc #20
|
|
ora #$20
|
|
rts
|
|
@rs_30:
|
|
sbc #30
|
|
ora #$30
|
|
rts
|
|
@rs_40:
|
|
sbc #40
|
|
ora #$40
|
|
rts
|
|
@rs_50:
|
|
sbc #50
|
|
ora #$50
|
|
rts
|
|
|
|
|
|
; get the current tick count, multiply it by 20, and return the lower 16 bits
|
|
; x*20 = x*16 + x*4
|
|
; inputs: none
|
|
; outputs: AX - tick count times 20 ('milliseconds')
|
|
mult20:
|
|
jsr _clock ; return current tick count in sreg:AX (high:low 16bits)
|
|
stx mult_temp_x ; remember high byte of lower 16bits
|
|
asl a
|
|
rol mult_temp_x
|
|
asl a
|
|
rol mult_temp_x
|
|
sta mult_temp
|
|
ldx mult_temp_x
|
|
stx mult_temp+1 ; mult_temp = ticks * 4
|
|
asl a
|
|
rol mult_temp_x
|
|
asl a
|
|
rol mult_temp_x ; mult_temp_x:A = 'ticks * 16'
|
|
clc ; AX - tick count * 16, mult_temp - tick count * 4
|
|
adc mult_temp
|
|
sta mult_temp
|
|
lda mult_temp+1
|
|
adc mult_temp_x
|
|
tax
|
|
lda mult_temp
|
|
rts
|
|
|
|
|
|
; get the current tick count, multiply it by 17, and return the lower 16 bits
|
|
; x*17 = x*16 + x
|
|
; inputs: none
|
|
; outputs: AX - tick count times 17 ('milliseconds')
|
|
mult17:
|
|
jsr _clock ; return current tick count in sreg:AX (high:low 16bits)
|
|
sta mult_temp
|
|
stx mult_temp+1
|
|
stx mult_temp_x
|
|
.repeat 4
|
|
asl a
|
|
rol mult_temp_x
|
|
.endrepeat ; mult_temp_x:A = 'ticks * 16'
|
|
clc
|
|
adc mult_temp
|
|
sta mult_temp
|
|
lda mult_temp+1
|
|
adc mult_temp_x
|
|
tax
|
|
lda mult_temp
|
|
rts
|
|
|
|
|
|
;-- LICENSE FOR clk_timer.s --
|
|
; The contents of this file are subject to the Mozilla Public License
|
|
; Version 1.1 (the "License"); you may not use this file except in
|
|
; compliance with the License. You may obtain a copy of the License at
|
|
; http://www.mozilla.org/MPL/
|
|
;
|
|
; Software distributed under the License is distributed on an "AS IS"
|
|
; basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
|
|
; License for the specific language governing rights and limitations
|
|
; under the License.
|
|
; -- LICENSE END --
|