OXYGENHUB
◆ main x16-emulator / src / ymglue.cpp
2.8 KiB · C++ · last changed chore(): initial commit 15 days ago source blame history raw
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#include "ymglue.h"
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#include "ymfm_opm.h"
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#include <cstdint>
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class ym2151_interface : public ymfm::ymfm_interface {
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	public:
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		ym2151_interface():
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			m_chip(*this),
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			m_timers{0, 0},
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			m_busy_timer{ 0 },
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			m_irq_status{ false }
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		{ }
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		~ym2151_interface() { }
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		virtual void ymfm_sync_mode_write(uint8_t data) override {
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			m_engine->engine_mode_write(data);
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		}
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		virtual void ymfm_sync_check_interrupts() override {
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			m_engine->engine_check_interrupts();
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		}
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		virtual void ymfm_set_timer(uint32_t tnum, int32_t duration_in_clocks) override {
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			if (tnum >= 2) return;
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			m_timers[tnum] = duration_in_clocks;
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		}
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		virtual void ymfm_set_busy_end(uint32_t clocks) override {
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			m_busy_timer = clocks;
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		}
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		virtual bool ymfm_is_busy() override {
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			return m_busy_timer > 0;
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		}
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		virtual void ymfm_update_irq(bool asserted) override {
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			m_irq_status = asserted;
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		}
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		void update_clocks(int cycles) {
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			m_busy_timer = std::max(0, m_busy_timer - (64 * cycles));
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			for (int i = 0; i < 2; ++i) {
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				if (m_timers[i] > 0) {
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					m_timers[i] = std::max(0, m_timers[i] - (64 * cycles));
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					if (m_timers[i] <= 0) {
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						m_engine->engine_timer_expired(i);
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					}
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				}
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			}
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		}
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		void write(uint8_t addr, uint8_t value) {
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			if (!ymfm_is_busy()) {
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				m_chip.write_address(addr);
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				m_chip.write_data(value);
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			} else {
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				printf("YM2151 write received while busy.\n");
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			}
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		}
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		void generate(int16_t* output, uint32_t numsamples) {
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			int s = 0;
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			int ls, rs;
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			update_clocks(numsamples);
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			for (uint32_t i = 0; i < numsamples; i++) {
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				m_chip.generate(&opm_out);
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				ls = opm_out.data[0];
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				rs = opm_out.data[1];
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				if (ls < -32768) ls = -32768;
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				if (ls > 32767) ls = 32767;
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				if (rs < -32768) rs = -32768;
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				if (rs > 32767) rs = 32767;
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				output[s++] = ls;
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				output[s++] = rs;
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			}
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		}
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		uint8_t read_status() {
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			return m_chip.read_status();
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		}
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		bool irq() {
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			return m_irq_status;
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		}
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	private:
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		ymfm::ym2151 m_chip;
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		int32_t m_timers[2];
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		int32_t m_busy_timer;
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		bool m_irq_status;
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		ymfm::ym2151::output_data opm_out;
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};
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namespace {
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	ym2151_interface opm_iface;
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	bool initialized = false;
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}
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extern "C" {
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	void YM_Create(int clock) {
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		// clock is fixed at 3.579545MHz
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	}
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	void YM_init(int sample_rate, int frame_rate) {
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		// args are ignored
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		initialized = true;
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	}
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	void YM_stream_update(uint16_t* output, uint32_t numsamples) {
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		if (initialized) opm_iface.generate((int16_t*)output, numsamples);
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	}
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	void YM_write_reg(uint8_t reg, uint8_t val) {
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		if (initialized) opm_iface.write(reg, val);
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	}
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	uint8_t YM_read_status() {
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		if (initialized)
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			return opm_iface.read_status();
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		else
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			return 0x00; // prevent programs that wait for the busy flag to clear from locking up (emulator compromise)
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	}
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	bool YM_irq() {
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		if (initialized)
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			return opm_iface.irq();
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		else
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			return false;
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	}
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}