SegaPCM: prepare to actually emulate it

CMakeLists.txt

@@ -365,6 +365,7 @@ src/engine/platform/sound/sn76496.cpp
 src/engine/platform/sound/ay8910.cpp
 src/engine/platform/sound/saa1099.cpp
 src/engine/platform/sound/namco.cpp
+src/engine/platform/sound/segapcm.cpp
 src/engine/platform/sound/gb/apu.c
 src/engine/platform/sound/gb/timing.c
 src/engine/platform/sound/pce_psg.cpp

src/engine/platform/segapcm.h

@@ -22,6 +22,7 @@
 
 #include "../dispatch.h"
 #include "../instrument.h"
+#include "sound/segapcm.h"
 #include <queue>
 
 class DivPlatformSegaPCM: public DivDispatch {
@@ -59,6 +60,7 @@ class DivPlatformSegaPCM: public DivDispatch {
       QueuedWrite(unsigned short a, unsigned char v): addr(a), val(v), addrOrVal(false) {}
     };
     std::queue<QueuedWrite> writes;
+    segapcm_device pcm;
     int delay;
     int pcmL, pcmR, pcmCycles;
     unsigned char sampleBank;

src/engine/platform/sound/segapcm.cpp

@@ -0,0 +1,125 @@
+// license:BSD-3-Clause
+// copyright-holders:Hiromitsu Shioya, Olivier Galibert
+/*********************************************************/
+/*    SEGA 16ch 8bit PCM                                 */
+/*********************************************************/
+
+#include <string.h>
+
+#include "segapcm.h"
+
+//-------------------------------------------------
+//  segapcm_device - constructor
+//-------------------------------------------------
+
+segapcm_device::segapcm_device()
+	: m_bankshift(12)
+	, m_bankmask(0x70)
+{
+}
+
+
+//-------------------------------------------------
+//  device_start - device-specific startup
+//-------------------------------------------------
+
+void segapcm_device::device_start()
+{
+        memset(m_ram,255,0x800);
+        memset(m_low,0,16);
+        memset(lastOut,0,16*2*sizeof(short));
+}
+
+
+//-------------------------------------------------
+//  sound_stream_update - handle a stream update
+//-------------------------------------------------
+
+void segapcm_device::sound_stream_update(int* outputs)
+{
+	/* clear the buffers */
+        outputs[0]=0;
+        outputs[1]=0;
+
+	// reg      function
+	// ------------------------------------------------
+	// 0x00     ?
+	// 0x01     ?
+	// 0x02     volume left
+	// 0x03     volume right
+	// 0x04     loop address (08-15)
+	// 0x05     loop address (16-23)
+	// 0x06     end address
+	// 0x07     address delta
+	// 0x80     ?
+	// 0x81     ?
+	// 0x82     ?
+	// 0x83     ?
+	// 0x84     current address (08-15), 00-07 is internal?
+	// 0x85     current address (16-23)
+	// 0x86     bit 0: channel disable?
+	//          bit 1: loop disable
+	//          other bits: bank
+	// 0x87     ?
+
+	/* loop over channels */
+	for (int ch = 0; ch < 16; ch++)
+	{
+		uint8_t *regs = &m_ram[8*ch];
+
+		/* only process active channels */
+		if (!(regs[0x86]&1))
+		{
+			int offset = (regs[0x86] & m_bankmask) << m_bankshift;
+			uint32_t addr = (regs[0x85] << 16) | (regs[0x84] << 8) | m_low[ch];
+			uint32_t loop = (regs[0x05] << 16) | (regs[0x04] << 8);
+			uint8_t end = regs[6] + 1;
+
+			int8_t v;
+                        bool fetch=true;
+
+			/* handle looping if we've hit the end */
+			if ((addr >> 16) == end)
+			{
+				if (regs[0x86] & 2)
+				{
+					regs[0x86] |= 1;
+                                        fetch=false;
+				}
+				else addr = loop;
+			}
+
+			/* fetch the sample */
+                        if (fetch) {
+                                v = read_byte(offset + (addr >> 8)) - 0x80;
+
+                                /* apply panning and advance */
+                                lastOut[ch][0]=v * (regs[2] & 0x7f);
+                                lastOut[ch][1]=v * (regs[3] & 0x7f);
+                                outputs[0]+=lastOut[ch][0];
+                                outputs[1]+=lastOut[ch][1];
+                                addr = (addr + regs[7]) & 0xffffff;
+                        } else {
+                          lastOut[ch][0]=0;
+                          lastOut[ch][1]=0;
+                        }
+
+			/* store back the updated address */
+			regs[0x84] = addr >> 8;
+			regs[0x85] = addr >> 16;
+			m_low[ch] = regs[0x86] & 1 ? 0 : addr;
+		}
+	}
+}
+
+
+void segapcm_device::write(unsigned int offset, uint8_t data)
+{
+	m_ram[offset & 0x07ff] = data;
+}
+
+
+uint8_t segapcm_device::read(unsigned int offset)
+{
+	return m_ram[offset & 0x07ff];
+}

src/engine/platform/sound/segapcm.h

@@ -0,0 +1,50 @@
+// license:BSD-3-Clause
+// copyright-holders:Hiromitsu Shioya, Olivier Galibert
+/*********************************************************/
+/*    SEGA 8bit PCM                                      */
+/*********************************************************/
+
+#ifndef MAMESOUND_SEGAPCM_H
+#define MAMESOUND_SEGAPCM_H
+
+#include <functional>
+
+//**************************************************************************
+//  TYPE DEFINITIONS
+//**************************************************************************
+
+class segapcm_device {
+public:
+	static constexpr int BANK_256    = 11;
+	static constexpr int BANK_512    = 12;
+	static constexpr int BANK_12M    = 13;
+	static constexpr int BANK_MASK7  = 0x70 << 16;
+	static constexpr int BANK_MASKF  = 0xf0 << 16;
+	static constexpr int BANK_MASKF8 = 0xf8 << 16;
+
+        short lastOut[16][2];
+
+	segapcm_device();
+
+	// configuration
+	void set_bank(int bank) { m_bankshift = (bank & 0xf); m_bankmask = (0x70|((bank >> 16) & 0xfc)); }
+        void set_read(std::function<unsigned char(unsigned int)> r) { read_byte = r; }
+
+	void write(unsigned int offset, uint8_t data);
+	uint8_t read(unsigned int offset);
+
+	// device-level overrides
+	void device_start();
+
+	// sound stream update overrides
+	void sound_stream_update(int* outputs);
+
+private:
+	uint8_t m_ram[0x800];
+	uint8_t m_low[16];
+	int m_bankshift;
+	int m_bankmask;
+        std::function<unsigned char(unsigned int)> read_byte;
+};
+
+#endif // MAMESOUND_SEGAPCM_H