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Add NCR7496 variant to sn76496.c
Switched the SMS and Game gear PSGs to use an XOR instead of XNOR feedback, but this needs further verification. Updated comments to show which chips are currently verified. Cleaned up comments.
This commit is contained in:
Jonathan Gevaryahu
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19bf1b46ea
commit
315b992f44
@ -11,21 +11,30 @@
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channel sound generator, with three squarewave channels and a noise/arbitrary
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duty cycle channel.
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Noise emulation for all chips should be accurate:
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SN76489 uses a 15-bit shift register with taps on bits D and E, output on E,
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XOR function; SN94624 is identical to SN76489.
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* It uses a 15-bit ring buffer for periodic noise/arbitrary duty cycle.
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SN76489A uses a 16-bit shift register with taps on bits D and E, output on F,
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XNOR function
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* It uses a 16-bit ring buffer for periodic noise/arbitrary duty cycle.
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SN76494 and SN76496 are PROBABLY identical in operation to the SN76489A
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* They have an audio input line which is mixed with the 4 channels of output.
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Sega Master System III/MD/Genesis PSG uses a 16-bit shift register with taps
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on bits C and F, output on F
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* It uses a 16-bit ring buffer for periodic noise/arbitrary duty cycle.
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Sega Game Gear PSG is identical to the SMS3/MD/Genesis one except it has an
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extra register for mapping which channels go to which speaker.
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Noise emulation for all verified chips should be accurate:
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** SN76489 uses a 15-bit shift register with taps on bits D and E, output on E,
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XOR function; SN94624 is identical to SN76489.
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It uses a 15-bit ring buffer for periodic noise/arbitrary duty cycle.
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** SN76489A uses a 16-bit shift register with taps on bits D and E, output on F,
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XNOR function
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It uses a 16-bit ring buffer for periodic noise/arbitrary duty cycle.
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** SN76494 and SN76496 are PROBABLY identical in operation to the SN76489A
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They have an audio input line which is mixed with the 4 channels of output.
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** Sega Master System III/MD/Genesis PSG uses a 16-bit shift register with taps
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on bits C and F, output on F
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It uses a 16-bit ring buffer for periodic noise/arbitrary duty cycle.
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(whether it uses an XOR or XNOR needs to be verified)
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** Sega Game Gear PSG is identical to the SMS3/MD/Genesis one except it has an
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extra register for mapping which channels go to which speaker.
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The register, connected to a z80 port, means:
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for bits 7 6 5 4 3 2 1 0
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L3 L2 L1 L0 R3 R2 R1 R0
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** NCR7496 (as used on the Tandy 1000) is similar to the SN76489 but with a
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different noise LFSR patttern: taps on bits A and E, output on E
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It uses a 15-bit ring buffer for periodic noise/arbitrary duty cycle.
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(all this chip's info needs to be verified)
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28/03/2005 : Sebastien Chevalier
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Update th SN76496Write func, according to SN76489 doc found on SMSPower.
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- On write with 0x80 set to 0, when LastRegister is other then TONE,
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@ -52,7 +61,7 @@
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16/11/2009 : Lord Nightmare
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Fix screeching in regulus: When summing together four equal channels, the
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size of the max amplitude per channel should be 1/4 of the max range, not
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1/3.
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1/3. Added NCR7496. Changed sega psg/gamegear from XNOR to XOR.
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TODO: * Implement a function for setting stereo regs for the game gear.
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Requires making the core support both mono and stereo, and have
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@ -63,9 +72,10 @@
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max of 4Mhz and 32 clocks per sample on the SN76489A.
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* Implement the T6W28; has registers in a weird order, needs writes
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to be 'sanitized' first. Also is stereo, similar to game gear.
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* Implement the NCR 7496; Is probably 100% compatible with SN76496,
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but the whitenoise taps could be different. Needs someone with a
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Tandy 1200 or whatever it was which uses this to run some tests.
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* Test the NCR7496; Smspower says the whitenoise taps are A and E,
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but this needs verification on real hardware.
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* Test the SMS PSG/Gamegear PSG to see whether it uses XOR or XNOR
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taps.
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* Factor out common code so that the SAA1099 can share some code.
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***************************************************************************/
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@ -109,6 +119,7 @@ INLINE sn76496_state *get_safe_token(const device_config *device)
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sound_get_type(device) == SOUND_SN76489A ||
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sound_get_type(device) == SOUND_SN76494 ||
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sound_get_type(device) == SOUND_SN94624 ||
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sound_get_type(device) == SOUND_NCR7496 ||
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sound_get_type(device) == SOUND_GAMEGEAR ||
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sound_get_type(device) == SOUND_SMSIII);
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return (sn76496_state *)device->token;
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@ -359,37 +370,42 @@ static void generic_start(const device_config *device, int feedbackmask, int noi
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static DEVICE_START( sn76489 )
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{
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generic_start(device, 0x4000, 0x03, FALSE);
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generic_start(device, 0x4000, 0x03, FALSE); // todo: verify; assumed to be the same as sn94624
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}
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static DEVICE_START( sn76489a )
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{
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generic_start(device, 0x8000, 0x06, TRUE);
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generic_start(device, 0x8000, 0x06, TRUE); // verified by plgdavid
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}
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static DEVICE_START( sn76494 )
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{
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generic_start(device, 0x8000, 0x06, TRUE);
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generic_start(device, 0x8000, 0x06, TRUE); // todo: verify; assumed to be the same as sn76489a
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}
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static DEVICE_START( sn76496 )
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{
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generic_start(device, 0x8000, 0x06, TRUE);
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generic_start(device, 0x8000, 0x06, TRUE); // todo: verify; assumed to be the same as sn76489a
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}
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static DEVICE_START( sn94624 )
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{
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generic_start(device, 0x4000, 0x03, FALSE);
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generic_start(device, 0x4000, 0x03, FALSE); // verified by plgdavid
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}
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static DEVICE_START( ncr7496 )
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{
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generic_start(device, 0x4000, 0x11, FALSE); // todo: verify; from smspower wiki
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}
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static DEVICE_START( gamegear )
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{
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generic_start(device, 0x8000, 0x09, TRUE);
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generic_start(device, 0x8000, 0x09, FALSE); // todo: verify; from smspower wiki
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}
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static DEVICE_START( smsiii )
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{
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generic_start(device, 0x8000, 0x09, TRUE);
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generic_start(device, 0x8000, 0x09, FALSE); // todo: verify; from smspower wiki
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}
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@ -428,16 +444,6 @@ DEVICE_GET_INFO( sn76489 )
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}
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}
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DEVICE_GET_INFO( sn94624 )
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{
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switch (state)
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{
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case DEVINFO_FCT_START: info->start = DEVICE_START_NAME( sn94624 ); break;
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case DEVINFO_STR_NAME: strcpy(info->s, "SN94624"); break;
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default: DEVICE_GET_INFO_CALL(sn76496); break;
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}
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}
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DEVICE_GET_INFO( sn76489a )
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{
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switch (state)
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@ -458,6 +464,26 @@ DEVICE_GET_INFO( sn76494 )
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}
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}
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DEVICE_GET_INFO( sn94624 )
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{
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switch (state)
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{
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case DEVINFO_FCT_START: info->start = DEVICE_START_NAME( sn94624 ); break;
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case DEVINFO_STR_NAME: strcpy(info->s, "SN94624"); break;
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default: DEVICE_GET_INFO_CALL(sn76496); break;
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}
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}
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DEVICE_GET_INFO( ncr7496 )
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{
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switch (state)
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{
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case DEVINFO_FCT_START: info->start = DEVICE_START_NAME( ncr7496 ); break;
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case DEVINFO_STR_NAME: strcpy(info->s, "NCR7496"); break;
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default: DEVICE_GET_INFO_CALL(sn76496); break;
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}
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}
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DEVICE_GET_INFO( gamegear )
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{
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switch (state)
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@ -11,6 +11,7 @@ DEVICE_GET_INFO( sn76489 );
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DEVICE_GET_INFO( sn76489a );
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DEVICE_GET_INFO( sn76494 );
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DEVICE_GET_INFO( sn94624 );
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DEVICE_GET_INFO( ncr7496 );
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DEVICE_GET_INFO( gamegear );
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DEVICE_GET_INFO( smsiii );
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@ -19,6 +20,7 @@ DEVICE_GET_INFO( smsiii );
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#define SOUND_SN76489A DEVICE_GET_INFO_NAME( sn76489a )
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#define SOUND_SN76494 DEVICE_GET_INFO_NAME( sn76494 )
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#define SOUND_SN94624 DEVICE_GET_INFO_NAME( sn94624 )
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#define SOUND_NCR7496 DEVICE_GET_INFO_NAME( ncr7496 )
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#define SOUND_GAMEGEAR DEVICE_GET_INFO_NAME( gamegear )
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#define SOUND_SMSIII DEVICE_GET_INFO_NAME( smsiii )
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