More DAC identification and Namco sound research (nw)

src/devices/sound/dac.h

@@ -292,6 +292,7 @@ DAC_GENERATOR(MC3410, mc3410_device, dac_word_interface, dac_code_binary<10>, da
 DAC_GENERATOR(PCM54HP, pcm54hp_device, dac_word_interface, dac_code_binary<16>, dac_gain_r2r, "PCM54HP", "pcm54hp")
 DAC_GENERATOR(UDA1341TS, uda1341ts_device, dac_word_interface, dac_code_twos_complement<16>, dac_gain_r2r, "UDA1341TS", "uda1341ts") // I2C stereo audio codec
 DAC_GENERATOR(ZN425E, zn425e_device, dac_byte_interface, dac_code_binary<8>, dac_gain_r2r, "ZN425E", "zn425e")
+DAC_GENERATOR(ZN429E, zn429e_device, dac_byte_interface, dac_code_binary<8>, dac_gain_r2r, "ZN429E-8", "zn429e")
 
 // DAC circuits/unidentified chips
 DAC_GENERATOR(DAC_1BIT, dac_1bit_device, dac_bit_interface, dac_code_binary<1>, 1.0, "1-Bit DAC", "dac")

src/devices/sound/namco.cpp

@@ -11,6 +11,16 @@
         - 8-voice mono (custom 15XX: Mappy, Dig Dug 2, etc)
         - 8-voice stereo (System 1)
 
+    The 15XX custom does not have a DAC of its own; instead, it streams
+    the 4-bit PROM data directly into the 99XX custom DAC. Most pre-99XX
+    (and pre-15XX) Namco games use a LS273 latch (cleared when sound is
+    disabled), a 4.7K/2.2K/1K/470 resistor-weighted DAC, and a 4066 and
+    second group of resistors (10K/22K/47K/100K) for volume control.
+    Pole Position does more complicated sound mixing: a 4051 multiplexes
+    wavetable sound with four signals derived from the 52XX and 54XX, the
+    selected signal is distributed to four volume control sections, and
+    finally the engine noise is mixed into all four channels.
+
 ***************************************************************************/
 
 #include "emu.h"

src/mame/drivers/byvid.cpp

@@ -13,7 +13,7 @@ board containing the video and sound cpus, and the video controller
 and the sound DAC and amp.
 
 Granny uses the MPU4 board, but it has a Vidiot Deluxe for the
-video, and a Cheep Squeek sound board. The manual incorrectly
+video, and a Cheap Squeek sound board. The manual incorrectly
 describes the babypac vidiot board, which is of little use.
 
 
@@ -794,7 +794,7 @@ static MACHINE_CONFIG_START( babypac, by133_state )
 
 	/* sound hardware */
 	MCFG_SPEAKER_STANDARD_MONO("speaker")
-	MCFG_SOUND_ADD("dac", DAC_8BIT_R2R, 0) MCFG_SOUND_ROUTE(ALL_OUTPUTS, "speaker", 0.25) // unknown DAC
+	MCFG_SOUND_ADD("dac", ZN429E, 0) MCFG_SOUND_ROUTE(ALL_OUTPUTS, "speaker", 0.25) // U32 (Vidiot) or U6 (Cheap Squeak)
 	MCFG_DEVICE_ADD("vref", VOLTAGE_REGULATOR, 0) MCFG_VOLTAGE_REGULATOR_OUTPUT(5.0)
 	MCFG_SOUND_ROUTE_EX(0, "dac", 1.0, DAC_VREF_POS_INPUT) MCFG_SOUND_ROUTE_EX(0, "dac", -1.0, DAC_VREF_NEG_INPUT)
 

src/mame/drivers/galaxian.cpp

@@ -6024,7 +6024,7 @@ static MACHINE_CONFIG_DERIVED( sfx, galaxian_base )
 	MCFG_AY8910_PORT_B_WRITE_CB(WRITE8(galaxian_state, sfx_sample_control_w))
 
 	/* DAC for the sample player */
-	MCFG_SOUND_ADD("dac", DAC_8BIT_R2R, 0) MCFG_SOUND_ROUTE(ALL_OUTPUTS, "speaker", 1.0) // unknown DAC
+	MCFG_SOUND_ADD("dac", DAC_8BIT_R2R, 0) MCFG_SOUND_ROUTE(ALL_OUTPUTS, "speaker", 1.0) // 16-pin IC (not identified by schematics)
 	MCFG_DEVICE_ADD("vref", VOLTAGE_REGULATOR, 0) MCFG_VOLTAGE_REGULATOR_OUTPUT(5.0)
 	MCFG_SOUND_ROUTE_EX(0, "dac", 1.0, DAC_VREF_POS_INPUT) MCFG_SOUND_ROUTE_EX(0, "dac", -1.0, DAC_VREF_NEG_INPUT)
 MACHINE_CONFIG_END

src/mame/drivers/junofrst.cpp

@@ -452,7 +452,7 @@ static MACHINE_CONFIG_START( junofrst, junofrst_state )
 	MCFG_SOUND_ROUTE(1, "filter.0.1", 0.30)
 	MCFG_SOUND_ROUTE(2, "filter.0.2", 0.30)
 
-	MCFG_SOUND_ADD("dac", DAC_8BIT_R2R, 0) MCFG_SOUND_ROUTE(ALL_OUTPUTS, "speaker", 0.25) // unknown DAC
+	MCFG_SOUND_ADD("dac", DAC_8BIT_R2R, 0) MCFG_SOUND_ROUTE(ALL_OUTPUTS, "speaker", 0.25) // 100K (R56-63)/200K (R64-71) ladder network
 	MCFG_DEVICE_ADD("vref", VOLTAGE_REGULATOR, 0) MCFG_VOLTAGE_REGULATOR_OUTPUT(5.0)
 	MCFG_SOUND_ROUTE_EX(0, "dac", 1.0, DAC_VREF_POS_INPUT) MCFG_SOUND_ROUTE_EX(0, "dac", -1.0, DAC_VREF_NEG_INPUT)
 

src/mame/drivers/mappy.cpp

@@ -14,9 +14,8 @@ They can be divided in three "families":
    The hardware consists of two 6809, and several Namco custom ICs that provide
    a static tilemap and 2bpp sprites.
    Grobda is the only Namco game of this era that has speech (just a short
-   sample). At this time, it is still unknown whether the DAC used to play
+   sample). At this time, it is still unknown how speech samples are transmitted
-   the speech is part of the standard Namco sound hardware, or a quick addition
+   to the DAC (almost certainly the same resistor network used by the 15XX).
-   to the base board.
 2) Phozon. This game runs on an unique board: the large number of sprites on
    screen at the same time required a 3rd 6809 to help with the calculations.
    The sprite hardware is also different from Super Pacman, featuring 8x8 sprites.
@@ -44,7 +43,8 @@ CPU board:
 15XX     sound control
 16XX     I/O control
 5xXX(x2) I/O
-99XX     sound volume (only Mappy, Super Pacman uses a standard LS273)
+99XX     DAC with volume control (only Mappy, Super Pacman uses LS273, CD4066
+         and binary-weighted resistors R34-37 and R22-25)
 
 Video board:
 00XX     tilemap address generator with scrolling capability (only Super Pacman)
@@ -1766,7 +1766,7 @@ static MACHINE_CONFIG_START( grobda, mappy_state )
 	MCFG_NAMCO56XX_OUT_0_CB(WRITE8(mappy_state, out_mux))
 
 	/* sound hardware */
-	MCFG_SOUND_ADD("dac", DAC_4BIT_R2R, 0) MCFG_SOUND_ROUTE(ALL_OUTPUTS, "speaker", 0.275) // unknown DAC
+	MCFG_SOUND_ADD("dac", DAC_4BIT_BINARY_WEIGHTED, 0) MCFG_SOUND_ROUTE(ALL_OUTPUTS, "speaker", 0.275) // alternate route to 15XX-related DAC?
 	MCFG_DEVICE_ADD("vref", VOLTAGE_REGULATOR, 0) MCFG_VOLTAGE_REGULATOR_OUTPUT(5.0)
 	MCFG_SOUND_ROUTE_EX(0, "dac", 1.0, DAC_VREF_POS_INPUT) MCFG_SOUND_ROUTE_EX(0, "dac", -1.0, DAC_VREF_NEG_INPUT)
 MACHINE_CONFIG_END
@@ -2412,13 +2412,13 @@ DRIVER_INIT_MEMBER(mappy_state,grobda)
 {
 	m_type = GAME_GROBDA;
 
-	/* I think the speech in Grobda is not a standard Namco sound feature, but rather a hack.
+	/* The speech in Grobda might not be a standard Namco sound feature, but rather a hack.
 	   The hardware automatically cycles the bottom 6 address lines of sound RAM, so they
 	   probably added a latch loaded when the bottom 4 lines are 0010 (which corresponds
 	   to locations not used by the sound hardware).
 	   The program writes the same value to 0x02, 0x12, 0x22 and 0x32.
 	   However, removing the 15XX from the board causes sound to disappear completely, so
-	   the DAC might be built-in after all.
+	   the 15XX may still play some part in conveying speech to the DAC.
 	  */
 	m_subcpu->space(AS_PROGRAM).install_write_handler(0x0002, 0x0002, write8_delegate(FUNC(dac_byte_interface::write), (dac_byte_interface *)m_dac));
 }

src/mame/drivers/namcos1.cpp

@@ -1068,8 +1068,8 @@ static MACHINE_CONFIG_START( ns1, namcos1_state )
 	MCFG_SOUND_ROUTE(0, "lspeaker", 0.50)
 	MCFG_SOUND_ROUTE(1, "rspeaker", 0.50)
 
-	MCFG_SOUND_ADD("dac0", DAC_8BIT_R2R, 0) MCFG_SOUND_ROUTE(ALL_OUTPUTS, "lspeaker", 0.5) MCFG_SOUND_ROUTE(ALL_OUTPUTS, "rspeaker", 0.5) // unknown DAC
+	MCFG_SOUND_ADD("dac0", DAC_8BIT_R2R, 0) MCFG_SOUND_ROUTE(ALL_OUTPUTS, "lspeaker", 0.5) MCFG_SOUND_ROUTE(ALL_OUTPUTS, "rspeaker", 0.5) // 10-pin 1Kx8R SIP with HC374 latch
-	MCFG_SOUND_ADD("dac1", DAC_8BIT_R2R, 0) MCFG_SOUND_ROUTE(ALL_OUTPUTS, "lspeaker", 0.5) MCFG_SOUND_ROUTE(ALL_OUTPUTS, "rspeaker", 0.5) // unknown DAC
+	MCFG_SOUND_ADD("dac1", DAC_8BIT_R2R, 0) MCFG_SOUND_ROUTE(ALL_OUTPUTS, "lspeaker", 0.5) MCFG_SOUND_ROUTE(ALL_OUTPUTS, "rspeaker", 0.5) // 10-pin 1Kx8R SIP with HC374 latch
 	MCFG_DEVICE_ADD("vref", VOLTAGE_REGULATOR, 0) MCFG_VOLTAGE_REGULATOR_OUTPUT(5.0)
 	MCFG_SOUND_ROUTE_EX(0, "dac0", 1.0, DAC_VREF_POS_INPUT) MCFG_SOUND_ROUTE_EX(0, "dac0", -1.0, DAC_VREF_NEG_INPUT)
 	MCFG_SOUND_ROUTE_EX(0, "dac1", 1.0, DAC_VREF_POS_INPUT) MCFG_SOUND_ROUTE_EX(0, "dac1", -1.0, DAC_VREF_NEG_INPUT)