sms.cpp: fix Out Run sound in FM mode [Enik Land]

src/devices/bus/sg1000_exp/fm_unit.cpp

@@ -11,13 +11,31 @@ Release data from the Sega Retro project:
 
 Notes:
 
-This emulation is based on Charles MacDonald's analysis of Enri's schematics
-of the FM unit hardware.
+The FM Unit add-on was released for the Mark III, so compatible games were
+released only for that console and the Japanese SMS, that has the FM chip
+built-in. The games play FM sound only when detect the FM hardware. The normal
+PSG sound is replaced, except when sampled voices, not supported by the FM
+chip, are played. Some games released for western SMS versions also contain FM
+code, that is played on a Mark III / SMSJ when connected through a cartridge
+adapter.
+
+The IO address map (read/write ports) is based on Charles MacDonald's analysis
+of Enri's schematics of the FM unit hardware.
 
 Any software that access controllers through IO ports $C0/$C1 instead $DC/$DD
 (the game Fushigi no Oshiro Pit Pot is a known example) has control problems
 when the FM Sound Unit is attached (real hardware behavior).
 
+TODO:
+
+- Confirm the assumption that PSG and FM sound are not mixed by the FM unit
+and there is only FM sound when the unit is enabled. Two evidences that were
+observed: every time a game with FM sound plays sampled voices through PSG,
+the game disables/enables the FM chip before/after playing the PSG sound, and
+a user reported, on the topic of the SMSPower Forums where the PSG/FM mixing
+control of the SMSJ was discovered, that the hack that adds FM sound to Sonic
+SMS version is not playing PSG sound on his Mark III with the FM unit.
+
 **********************************************************************/
 
 #include "fm_unit.h"
@@ -33,6 +51,8 @@ const device_type SEGA_FM_UNIT = &device_creator<sega_fm_unit_device>;
 
 static MACHINE_CONFIG_FRAGMENT( fm_config )
 	MCFG_SOUND_ADD("ym2413", YM2413, XTAL_10_738635MHz/3)
+	// if this output gain is changed, the gain set when unmute the output need
+	// to be changed too, probably along the gain set for SMSJ/SMSKRFM drivers.
 	MCFG_SOUND_ROUTE(ALL_OUTPUTS, ":mono", 1.00)
 MACHINE_CONFIG_END
 
@@ -56,6 +76,7 @@ sega_fm_unit_device::sega_fm_unit_device(const machine_config &mconfig, const ch
 	device_t(mconfig, SEGA_FM_UNIT, "Sega FM Sound Unit", tag, owner, clock, "sega_fm_unit", __FILE__),
 	device_sg1000_expansion_slot_interface(mconfig, *this),
 	m_ym(*this, "ym2413"),
+	m_psg(*this, ":segapsg"),
 	m_audio_control(0)
 {
 }
@@ -78,6 +99,8 @@ void sega_fm_unit_device::device_start()
 
 READ8_MEMBER(sega_fm_unit_device::peripheral_r)
 {
+	// the value previously written to the control port is returned on all
+	// active read offsets.
 	if (offset <= 3)
 	{
 		return m_audio_control & 0x01;
@@ -95,20 +118,28 @@ WRITE8_MEMBER(sega_fm_unit_device::peripheral_w)
 	switch (offset)
 	{
 		case 0: // register port
-			if (m_audio_control == 0x01)
-			{
-				m_ym->write(space, 0, data & 0x3f);
-			}
+			m_ym->write(space, 0, data & 0x3f);
 			break;
 		case 1: // data port
-			if (m_audio_control == 0x01)
-			{
-				m_ym->write(space, 1, data);
-			}
+			m_ym->write(space, 1, data);
 			break;
 		case 2: // control port
 		case 3: // mirror
 			m_audio_control = data & 0x01;
+			if (m_audio_control == 0x01)
+			{
+				m_ym->set_output_gain(0, 1.0);
+				// assume the PSG output is muted when FM is active.
+				// Out Run need this. Needs confirmation (see TODO).
+				if (m_psg.found())
+					m_psg->set_output_gain(0, 0.0);
+			}
+			else
+			{
+				m_ym->set_output_gain(0, 0.0);
+				if (m_psg.found())
+					m_psg->set_output_gain(0, 1.0);
+			}
 			break;
 		default:
 			break;

src/devices/bus/sg1000_exp/fm_unit.h

@@ -14,6 +14,7 @@
 
 #include "emu.h"
 #include "sound/ym2413.h"
+#include "sound/sn76496.h"
 #include "sg1000exp.h"
 
 
@@ -44,6 +45,7 @@ protected:
 
 private:
 	required_device<ym2413_device> m_ym;
+	optional_device<segapsg_device> m_psg;
 	UINT8 m_audio_control;
 };
 

src/mame/drivers/sms.cpp

@@ -890,6 +890,8 @@ static MACHINE_CONFIG_DERIVED( smsj, sms1_kr )
 	MCFG_CPU_IO_MAP(smsj_io)
 
 	MCFG_SOUND_ADD("ym2413", YM2413, XTAL_10_738635MHz/3)
+	// if this output gain is changed, the gain set when unmute the output need
+	// to be changed too, probably along the gain set for the Mark III FM Unit.
 	MCFG_SOUND_ROUTE(ALL_OUTPUTS, "mono", 1.00)
 MACHINE_CONFIG_END
 

src/mame/machine/sms.cpp

@@ -458,6 +458,22 @@ READ8_MEMBER(sms_state::sms_input_port_dd_r)
 WRITE8_MEMBER(sms_state::smsj_audio_control_w)
 {
 	m_smsj_audio_control = data & 0x03;
+
+	/*  Mute settings:
+		0,0 : PSG only (power-on default)
+		0,1 : FM only
+		1,0 : Both PSG and FM disabled
+		1,1 : Both PSG and FM enabled 
+	*/
+	if (m_smsj_audio_control == 0x00 || m_smsj_audio_control == 0x03)
+		m_psg_sms->set_output_gain(0, 1.0);
+	else
+		m_psg_sms->set_output_gain(0, 0.0);
+
+	if (m_smsj_audio_control == 0x01 || m_smsj_audio_control == 0x03)
+		m_ym->set_output_gain(0, 1.0);
+	else
+		m_ym->set_output_gain(0, 0.0);
 }
 
 
@@ -492,29 +508,19 @@ READ8_MEMBER(sms_state::smsj_audio_control_r)
 
 WRITE8_MEMBER(sms_state::smsj_ym2413_register_port_w)
 {
-	if (m_smsj_audio_control == 0x01 || m_smsj_audio_control == 0x03)
-		m_ym->write(space, 0, data & 0x3f);
+	m_ym->write(space, 0, data & 0x3f);
 }
 
 
 WRITE8_MEMBER(sms_state::smsj_ym2413_data_port_w)
 {
-	if (m_smsj_audio_control == 0x01 || m_smsj_audio_control == 0x03)
-	{
-		//logerror("data_port_w %x %x\n", offset, data);
-		m_ym->write(space, 1, data);
-	}
+	//logerror("data_port_w %x %x\n", offset, data);
+	m_ym->write(space, 1, data);
 }
 
 
 WRITE8_MEMBER(sms_state::sms_psg_w)
 {
-	if (m_is_smsj)
-	{
-		if (m_smsj_audio_control != 0x00 && m_smsj_audio_control != 0x03)
-			return;
-	}
-
 	m_psg_sms->write(space, offset, data, mem_mask);
 }