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https://github.com/lscharen/iigs-game-engine.git
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Optimization to avoid recalculating DOC frequencies when APU value does not change
This commit is contained in:
Lucas Scharenbroich
parent
bdb4006e22
commit
a1261e8339
@ -587,6 +587,9 @@ interrupt_handler = *
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cmp #8
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bcc :mute_pulse1
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cmp _apu_pulse1_last_period ; it's expensive to recalc frequencies, so avoid it when possible
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beq :freq_end_pulse1
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sta _apu_pulse1_last_period
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jsr get_pulse_freq ; return freq in 16-bit accumulator
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sep #$30
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ldx #$00+pulse1_oscillator
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@ -596,6 +599,7 @@ interrupt_handler = *
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stx sound_address
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xba
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sta sound_data
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:freq_end_pulse1 sep #$30 ; redundent, but avoids extra branches
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lda #$80+pulse1_oscillator
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sta sound_address
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@ -627,6 +631,9 @@ interrupt_handler = *
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cmp #8
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bcc :mute_pulse2
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cmp _apu_pulse2_last_period
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beq :freq_end_pulse2
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sta _apu_pulse2_last_period
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jsr get_pulse_freq ; return freq in 16-bic accumulator
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sep #$30
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ldx #$00+pulse2_oscillator
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@ -636,6 +643,7 @@ interrupt_handler = *
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stx sound_address
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xba
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sta sound_data
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:freq_end_pulse2 sep #$30
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lda #$80+pulse2_oscillator
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sta sound_address
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@ -676,6 +684,9 @@ interrupt_handler = *
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; Man's stage. At the expense of accuracy, these can be eliminated in an emulator e.g. by halting the
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; triangle channel when an ultrasonic frequency is set (a timer value less than 2).
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cmp _apu_triangle_last_period
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beq :freq_end_triangle
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sta _apu_triangle_last_period
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jsr get_pulse_freq ; return freq in 16-bic accumulator
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lsr
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sep #$30
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@ -686,6 +697,7 @@ interrupt_handler = *
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stx sound_address
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xba
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sta sound_data
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:freq_end_triangle sep #$30
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lda #$40+triangle_oscillator
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sta sound_address
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@ -701,23 +713,17 @@ interrupt_handler = *
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; Now the noise channel. It's mixer volume output is ~half of the pulse channels
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lda #$40+noise_oscillator
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sta sound_address
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lda APU_NOISE_LENGTH_COUNTER ; If the length counter is zero, no output
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beq :set_volume_noise
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lda APU_NOISE_REG1
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bit #NOISE_CONST_VOL_FLAG ; Check the constant volume bit
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bne :set_volume_noise
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lda APU_NOISE_ENVELOPE
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:set_volume_noise
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jsr set_pulse_volume
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beq :mute_noise
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rep #$30
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lda APU_NOISE_CURRENT_PERIOD
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cmp _apu_noise_last_period ; it's expensive to recalc frequencies, so avoid it when possible
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beq :freq_end_noise
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sta _apu_noise_last_period
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jsr get_pulse_freq ; return freq in 16-bic accumulator
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sep #$30
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ldx #$00+noise_oscillator
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stx sound_address
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sta sound_data
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@ -725,9 +731,23 @@ interrupt_handler = *
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stx sound_address
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xba
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sta sound_data
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:freq_end_noise sep #$30
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lda #$40+noise_oscillator
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sta sound_address
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lda APU_NOISE_REG1
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bit #NOISE_CONST_VOL_FLAG ; Check the constant volume bit
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bne :set_volume_noise
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lda APU_NOISE_ENVELOPE
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bra :set_volume_noise
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:mute_noise
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sep #$30
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lda #$40+noise_oscillator
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sta sound_address
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lda #0
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:set_volume_noise jsr set_pulse_volume
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:not_timer
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sep #$30
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lda #0
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jsr setborder
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@ -817,49 +837,11 @@ turn_off_interrupts
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apu_frame_counter dw 0 ; frame counter, clocked at 240Hz from the interrupt handler
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; Internal APU register offsets
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;length_counter_halt equ 0
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;length_counter equ 1
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;constant_volume_flag equ 2
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;volume equ 3
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;current_period equ 4
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;target_period equ 6
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; Internal APU registers for channel 1
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;apu_pulse1 ds 8
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;apu_pulse2 ds 8
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;apu_pulse1_length_counter dfb 0
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;apu_pulse1_decay_level dfb 0
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;apu_pulse1_current_period dw 0
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;apu_pulse2_length_counter dfb 0
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;apu_pulse2_decay_level dfb 0
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;apu_pulse2_current_period dw 0
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duty_cycle_page dfb $01,$02,$03,$04 ; Page of DOC RAM that holds the different duty cycle wavforms
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border_color dw 0
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dividend dw 0
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dividend dw 0 ; Used when converting from NES APU values to DOC values
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divisor dw 0
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last_phase1_duty_cycle dfb $ff
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last_phase2_duty_cycle dfb $ff
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; 8-bit mode
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; A = register number
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; X = register value
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mx %00
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SetDOCReg
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stal $E0C03E
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txa
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stal $E0C03D
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rts
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_SetDOCReg mac
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lda ]1 ; Select the oscillator enable registers
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ldx ]2
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jsr SetDOCReg
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<<<
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; Pulse Channel 1
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APU_PULSE1
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APU_PULSE1_REG1 ds 1 ; DDLC NNNN - Duty, length counter halt, constant volume/evelope, envelope period/volume
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@ -877,7 +859,7 @@ APU_PULSE1_START_FLAG dfb 0
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APU_PULSE1_ENVELOPE_DIVIDER dfb 0
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APU_PULSE1_ENVELOPE dfb 0
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_apu_pulse1_last_period dw 0 ; optimization
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_apu_pulse1_last_period dw $FFFF ; optimization
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APU_PULSE2
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@ -896,7 +878,7 @@ APU_PULSE2_START_FLAG dfb 0
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APU_PULSE2_ENVELOPE_DIVIDER dfb 0
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APU_PULSE2_ENVELOPE dfb 0
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_apu_pulse2_last_period dw 0 ; optimization
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_apu_pulse2_last_period dw $FFFF ; optimization
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APU_TRIANGLE
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@ -910,6 +892,8 @@ APU_TRIANGLE_CURRENT_PERIOD dw 0
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APU_TRIANGLE_START_FLAG dfb 0
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APU_TRIANGLE_LINEAR_COUNTER dfb 0
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_apu_triangle_last_period dw $FFFF ; optimization
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APU_NOISE
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APU_NOISE_REG1 ds 1 ; --LC NNNN - length counter halt, constant volume/evelope, envelope period/volume
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@ -927,6 +911,9 @@ APU_NOISE_START_FLAG dfb 0
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APU_NOISE_ENVELOPE_DIVIDER dfb 0
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APU_NOISE_ENVELOPE dfb 0
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_apu_noise_last_period dw $FFFF ; optimization
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APU_STATUS ds 1
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mx %11
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