mirror of https://github.com/bsnes-emu/bsnes.git
118 lines
2.3 KiB
C++
118 lines
2.3 KiB
C++
void APU::DMC::start() {
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if(length_counter == 0) {
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read_addr = 0x4000 + (addr_latch << 6);
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length_counter = (length_latch << 4) + 1;
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}
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}
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void APU::DMC::stop() {
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length_counter = 0;
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dma_delay_counter = 0;
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cpu.set_rdy_line(1);
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cpu.set_rdy_addr(false);
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}
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uint8 APU::DMC::clock() {
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uint8 result = dac_latch;
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if(dma_delay_counter > 0) {
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dma_delay_counter--;
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if(dma_delay_counter == 1) {
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cpu.set_rdy_addr(true, 0x8000 | read_addr);
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} else if(dma_delay_counter == 0) {
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cpu.set_rdy_line(1);
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cpu.set_rdy_addr(false);
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dma_buffer = cpu.mdr();
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have_dma_buffer = true;
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length_counter--;
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read_addr++;
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if(length_counter == 0) {
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if(loop_mode) {
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start();
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} else if(irq_enable) {
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irq_pending = true;
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apu.set_irq_line();
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}
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}
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}
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}
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if(--period_counter == 0) {
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if(have_sample) {
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signed delta = (((sample >> bit_counter) & 1) << 2) - 2;
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unsigned data = dac_latch + delta;
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if((data & 0x80) == 0) dac_latch = data;
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}
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if(++bit_counter == 0) {
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if(have_dma_buffer) {
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have_sample = true;
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sample = dma_buffer;
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have_dma_buffer = false;
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} else {
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have_sample = false;
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}
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}
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period_counter = ntsc_dmc_period_table[period];
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}
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if(length_counter > 0 && have_dma_buffer == false && dma_delay_counter == 0) {
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cpu.set_rdy_line(0);
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dma_delay_counter = 4;
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}
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return result;
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}
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void APU::DMC::power() {
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}
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void APU::DMC::reset() {
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length_counter = 0;
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irq_pending = 0;
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period = 0;
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period_counter = ntsc_dmc_period_table[0];
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irq_enable = 0;
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loop_mode = 0;
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dac_latch = 0;
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addr_latch = 0;
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length_latch = 0;
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read_addr = 0;
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dma_delay_counter = 0;
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bit_counter = 0;
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have_dma_buffer = 0;
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dma_buffer = 0;
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have_sample = 0;
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sample = 0;
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}
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void APU::DMC::serialize(serializer& s) {
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s.integer(length_counter);
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s.integer(irq_pending);
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s.integer(period);
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s.integer(period_counter);
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s.integer(irq_enable);
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s.integer(loop_mode);
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s.integer(dac_latch);
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s.integer(addr_latch);
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s.integer(length_latch);
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s.integer(read_addr);
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s.integer(dma_delay_counter);
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s.integer(bit_counter);
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s.integer(have_dma_buffer);
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s.integer(dma_buffer);
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s.integer(have_sample);
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s.integer(sample);
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}
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