mm5837: unify implementations

* create base mm5837_source device to provide raw output
* mm5837_device is based on it
* mm5837_stream_device generates a sound stream from it
* frequency calculation now computed instead of table-based

src/devices/sound/mm5837.cpp

@@ -12,22 +12,16 @@
 #include "mm5837.h"
 
 
-//**************************************************************************
-//  CONSTEXPR DEFINITIONS
-//**************************************************************************
-
-constexpr int mm5837_device::m_frequency[];
-
-
 //**************************************************************************
 //  DEVICE DEFINITIONS
 //**************************************************************************
 
 DEFINE_DEVICE_TYPE(MM5837, mm5837_device, "mm5837", "MM5837 Digital Noise Source")
+DEFINE_DEVICE_TYPE(MM5837_STREAM, mm5837_stream_device, "mm5837", "MM5837 Digital Noise Stream")
 
 
 //**************************************************************************
-//  LIVE DEVICE
+//  MM5837 DEVICE
 //**************************************************************************
 
 //-------------------------------------------------
@@ -37,12 +31,12 @@ DEFINE_DEVICE_TYPE(MM5837, mm5837_device, "mm5837", "MM5837 Digital Noise Source
 mm5837_device::mm5837_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) :
 	device_t(mconfig, MM5837, tag, owner, clock),
 	m_output_cb(*this),
-	m_vdd(0),
 	m_timer(nullptr),
-	m_shift(0)
+	m_vdd(-12)
 {
 }
 
+
 //-------------------------------------------------
 //  device_start - device-specific startup
 //-------------------------------------------------
@@ -56,36 +50,70 @@ void mm5837_device::device_start()
 	m_timer = timer_alloc(0);
 
 	// register for save states
-	save_item(NAME(m_shift));
+	save_item(NAME(m_source.m_shift));
 }
 
+
 //-------------------------------------------------
 //  device_reset - device-specific reset
 //-------------------------------------------------
 
 void mm5837_device::device_reset()
 {
-	// initialize with something
+	m_source.reset();
-	m_shift = 123456;
 
 	if (m_vdd < 16)
-		m_timer->adjust(attotime::zero, 0, attotime::from_hz(m_frequency[m_vdd]));
+		m_timer->adjust(attotime::zero, 0, attotime::from_hz(mm5837_source::frequency(m_vdd)));
 	else
 		throw emu_fatalerror("%s: Invalid voltage: %d\n", tag(), m_vdd);
 }
 
+
 //-------------------------------------------------
 //  device_timer - handle timer callbacks
 //-------------------------------------------------
 
 void mm5837_device::device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr)
 {
-	int tap_14 = BIT(m_shift, 13);
+	m_output_cb(m_source.clock());
-	int tap_17 = BIT(m_shift, 16);
+}
-	int zero = (m_shift == 0) ? 1 : 0;
+
-
+
-	m_shift <<= 1;
+
-	m_shift |= tap_14 ^ tap_17 ^ zero;
+//**************************************************************************
-
+//  MM5837 STREAM DEVICE
-	m_output_cb(BIT(m_shift, 16));
+//**************************************************************************
+
+//-------------------------------------------------
+//  mm5837_stream_device - constructor
+//-------------------------------------------------
+
+mm5837_stream_device::mm5837_stream_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) :
+	device_t(mconfig, MM5837_STREAM, tag, owner, clock),
+	device_sound_interface(mconfig, *this),
+	m_stream(nullptr),
+	m_vdd(-12)
+{
+}
+
+
+//-------------------------------------------------
+//  device_start - device-specific startup
+//-------------------------------------------------
+
+void mm5837_stream_device::device_start()
+{
+	m_stream = stream_alloc(0, 1, mm5837_source::frequency(m_vdd));
+	save_item(NAME(m_source.m_shift));
+}
+
+
+//-------------------------------------------------
+//  sound_stream_update - fill the sound buffer
+//-------------------------------------------------
+
+void mm5837_stream_device::sound_stream_update(sound_stream &stream, std::vector<read_stream_view> const &inputs, std::vector<write_stream_view> &outputs)
+{
+	for (int sampindex = 0; sampindex < outputs[0].samples(); sampindex++)
+		outputs[0].put(sampindex, m_source.clock() ? 1.0 : 0.0);
 }

src/devices/sound/mm5837.h

@@ -94,6 +94,66 @@
 //  TYPE DEFINITIONS
 //**************************************************************************
 
+// ======================> mm5837_source
+
+class mm5837_source
+{
+public:
+	// construction/destruction
+	mm5837_source() :
+		m_shift(0x1ffff)
+	{
+	}
+
+	// reset to base state
+	void reset()
+	{
+		m_shift = 0x1ffff;
+	}
+
+	// clock one time and return the shift value
+	u8 clock()
+	{
+		int tap_14 = BIT(m_shift, 13);
+		int tap_17 = BIT(m_shift, 16);
+		int zero = (m_shift == 0) ? 1 : 0;
+
+		m_shift <<= 1;
+		m_shift |= tap_14 ^ tap_17 ^ zero;
+
+		return BIT(m_shift, 16);
+	}
+
+	// taken from the book 'mims circuit scrapbook, vol. 1'
+	static u32 frequency(double vdd)
+	{
+		// Vdd should be negative -6.2..-15V
+        if (vdd > -6.2 || vdd < -15)
+            throw emu_fatalerror("mm5837 frequency should be -6.2V .. -15V");
+
+        // curve fitting done in excel from this table:
+        // { 0, 0, 0, 0, 0, 0, 1, 2267, 8731, 16382, 23531, 32564, 38347, 40010, 37800, 33173 }
+        double result = 191.98*vdd*vdd*vdd + 5448.4*vdd*vdd + 43388*vdd + 105347;
+
+        // datasheet claims frequency range 24-56kHz at Vdd=-14V, but also lists
+        // maximum cycle times as ranging from 1.1-2.4s; since the 17-bit shift
+        // register cycles after 131072 clocks, we would expect the actual cycle
+        // times to be 2.34-5.46s at the 24-56kHz frequency range, so I'm presuming
+        // that it ticks 2x per "clock", effectively running at 2x the frequency
+        result *= 2;
+
+        // make sure the result isn't TOO crazy
+        result = std::max(result, 100.0);
+		return u32(result);
+	}
+
+	// leave this public for easy saving
+	u32 m_shift;
+};
+
+
+// ======================> mm5837_device
+
 class mm5837_device : public device_t
 {
 public:
@@ -101,7 +161,7 @@ public:
 	mm5837_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock = 0);
 
 	// configuration
-	void set_vdd_voltage(int voltage) { m_vdd = voltage; }
+	void set_vdd(double voltage) { m_vdd = voltage; }
 	auto output_callback() { return m_output_cb.bind(); }
 
 protected:
@@ -111,24 +171,42 @@ protected:
 	virtual void device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr) override;
 
 private:
-	// taken from the book 'mims circuit scrapbook, vol. 1'
+    // internal state
-	// this is the frequency the chip runs at when given a vdd voltage of -0 to -15
+	devcb_write_line m_output_cb;     // output callback
-	static constexpr int m_frequency[16] = { 0, 0, 0, 0, 0, 0, 1, 2267, 8731, 16382, 23531, 32564, 38347, 40010, 37800, 33173 };
+    emu_timer *m_timer;               // output timer
-
+    double m_vdd;                     // configured voltage
-	// callbacks
+	mm5837_source m_source;           // noise source
-	devcb_write_line m_output_cb;
-
-	// voltage (as positive number)
-	int m_vdd;
-
-	// output timer
-	emu_timer *m_timer;
-
-	// state
-	uint32_t m_shift;
 };
 
-// device type definition
+
+// ======================> mm5837_stream_device
+
+class mm5837_stream_device : public device_t, public device_sound_interface
+{
+public:
+	// construction/destruction
+	mm5837_stream_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
+
+	// configuration
+	void set_vdd(double voltage) { m_vdd = voltage; }
+
+protected:
+	// device-level overrides
+	virtual void device_start() override;
+
+	// sound stream update overrides
+	virtual void sound_stream_update(sound_stream &stream, std::vector<read_stream_view> const &inputs, std::vector<write_stream_view> &outputs) override;
+
+private:
+	sound_stream *m_stream;           // sound stream
+    double m_vdd;                     // configured voltage
+    mm5837_source m_source;           // noise source
+};
+
+
+// device type definitions
 DECLARE_DEVICE_TYPE(MM5837, mm5837_device)
+DECLARE_DEVICE_TYPE(MM5837_STREAM, mm5837_stream_device)
+
 
 #endif // MAME_SOUND_MM5837_H

src/mame/audio/sente6vb.cpp

@@ -55,6 +55,7 @@
 ***************************************************************************/
 
 #include "emu.h"
+#include "sound/mm5837.h"
 #include "audio/sente6vb.h"
 #include "cpu/z80/z80.h"
 #include "machine/clock.h"
@@ -66,53 +67,6 @@
 DEFINE_DEVICE_TYPE(SENTE6VB, sente6vb_device, "sente6vb", "Bally Sente 6VB Audio Board")
 
 
-/*************************************
-*
-*  Trivial sound device to spew
-*  a MM5837 noise stream to CEM3394
-*  inputs
-*
-*************************************/
-
-DECLARE_DEVICE_TYPE(MM5837_NOISE_SOURCE, mm5837_noise_source)
-
-class mm5837_noise_source : public device_t, public device_sound_interface
-{
-public:
-	mm5837_noise_source(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) :
-		device_t(mconfig, MM5837_NOISE_SOURCE, tag, owner, clock),
-		device_sound_interface(mconfig, *this),
-		m_stream(nullptr),
-		m_noise_state(0x1ffff)
-	{
-	}
-
-protected:
-	// device-level overrides
-	virtual void device_start() override
-	{
-		m_stream = stream_alloc(0, 1, clock());
-		save_item(NAME(m_noise_state));
-	}
-
-	// sound stream update overrides
-	virtual void sound_stream_update(sound_stream &stream, std::vector<read_stream_view> const &inputs, std::vector<write_stream_view> &outputs) override
-	{
-		for (int sampindex = 0; sampindex < outputs[0].samples(); sampindex++)
-		{
-			outputs[0].put(sampindex, BIT(m_noise_state, 0) ? 1.0 : 0.0);
-			m_noise_state = (m_noise_state >> 1) | ((BIT(m_noise_state, 0) ^ BIT(m_noise_state, 3)) << 16);
-		}
-	}
-
-private:
-	sound_stream *m_stream;           // sound stream
-	u32 m_noise_state;                // noise state
-};
-
-DEFINE_DEVICE_TYPE(MM5837_NOISE_SOURCE, mm5837_noise_source, "mm5837noise", "MM5837")
-
-
 
 /*************************************
  *
@@ -172,7 +126,9 @@ void sente6vb_device::device_add_mconfig(machine_config &config)
 
 	SPEAKER(config, "mono").front_center();
 
-	mm5837_noise_source &noise(MM5837_NOISE_SOURCE(config, "noise", 100000));
+	mm5837_stream_device &noise(MM5837_STREAM(config, "noise", 0));
+//	noise.set_vdd(-6.5);   // seems too low -- possible the mapping in mm5837 is wrong
+	noise.set_vdd(-8.0);
 
 	for (auto &cem_device : m_cem_device)
 	{
@@ -180,7 +136,7 @@ void sente6vb_device::device_add_mconfig(machine_config &config)
 		cem_device->set_vco_zero_freq(431.894);
 		cem_device->set_filter_zero_freq(1300.0);
 		cem_device->add_route(ALL_OUTPUTS, "mono", 0.90);
-		noise.add_route(0, *cem_device, 1.0);
+		noise.add_route(0, *cem_device, 0.5);
 	}
 }
 

src/mame/drivers/beezer.cpp

@@ -554,7 +554,7 @@ void beezer_state::beezer(machine_config &config)
 	// schematics show an input labeled VCO to channel 2, but the source is unknown
 
 	mm5837_device &noise(MM5837(config, "noise"));
-	noise.set_vdd_voltage(12);
+	noise.set_vdd(-12);
 	noise.output_callback().set(FUNC(beezer_state::noise_w));
 
 	SPEAKER(config, "speaker").front_center();