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https://github.com/holub/mame
synced 2025-05-29 00:53:09 +03:00
Fixed sn76489a periodic noise once again (and simplified a bit of code), now should be closer to or match real chips as sampled.
Added true clock divider emulation, so emulation may be a bit slower. [Lord Nightmare, PlgDavid, Kold666]
This commit is contained in:
Jonathan Gevaryahu
parent
730d70ee06
commit
f79dfb098a
@ -19,8 +19,10 @@
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** SN76489A uses a 15-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 15-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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** SN76494 is the same as SN76489A but lacks the /8 divider on its clock input.
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** SN76496 is PROBABLY identical in operation to the SN76489A, need more info.
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All the SN7xxxx chips have an audio input line which is mixed with the 4 channels
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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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@ -70,24 +72,23 @@
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based on testing. Got rid of R->OldNoise and fixed taps accordingly.
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Added stereo support for game gear.
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11/15/2010 : Lord Nightmare
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15/01/2010 : Lord Nightmare
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Fix an issue with SN76489 and SN76489A having the wrong periodic noise periods.
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Note that properly emulating the noise cycle bit timing accurately may require
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extensive rewriting.
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24/01/2010: Lord Nightmare
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Implement periodic noise as forcing one of the XNOR or XOR taps to 1 or 0 respectively.
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Thanks to PlgDavid for providing samples which helped immensely here.
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Added true clock divider emulation, so sn94624 and sn76494 run 8x faster than
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the others, as in real life.
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TODO: * Implement the TMS9919 which is an earlier version, possibly
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lacking the /8 clock divider, of the SN76489, and hence would
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have a max clock of 500Khz and 4 clocks per sample, as opposed to
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max of 4Mhz and 32 clocks per sample on the SN76489A.
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TODO: * Implement the TMS9919 - any difference to sn94624?
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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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* 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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* Factor out common code so that the SAA1099 can share some code.
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* Implement periodic noise as using a pointer to a table rather than a
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self feeding lfsr. Kold666's recording of dorunrun proves this is the
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right way.
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* Fix the whitenoise bit timing so that dorunrun matches Kold666's PCB sample.
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***************************************************************************/
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#include "emu.h"
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@ -96,7 +97,6 @@
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#define MAX_OUTPUT 0x7fff
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// make the above 0x3fff if using bipolar output
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#define NOISEMODE (R->Register[6]&4)?1:0
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@ -109,8 +109,11 @@ struct _sn76496_state
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INT32 LastRegister; /* last register written */
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INT32 Volume[4]; /* db volume of voice 0-2 and noise */
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UINT32 RNG; /* noise generator LFSR*/
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INT32 ClockDivider; /* clock divider */
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INT32 CurrentClock;
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INT32 FeedbackMask; /* mask for feedback */
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INT32 WhitenoiseTaps; /* mask for white noise taps */
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INT32 WhitenoiseTap1; /* mask for white noise tap 1 (higher one, usually bit 14) */
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INT32 WhitenoiseTap2; /* mask for white noise tap 2 (lower one, usually bit 13)*/
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INT32 FeedbackInvert; /* feedback invert flag (xor vs xnor) */
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INT32 Negate; /* output negate flag */
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INT32 Stereo; /* whether we're dealing with stereo or not */
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@ -207,11 +210,11 @@ WRITE8_DEVICE_HANDLER( sn76496_w )
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break;
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case 6: /* noise : frequency, mode */
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{
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if ((data & 0x80) == 0) R->Register[r] = (R->Register[r] & 0x3f0) | (data & 0x0f);
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if ((data & 0x80) == 0) logerror("sn76489: write to reg 6 with bit 7 clear; data was %03x, new write is %02x! report this to LN!\n", R->Register[6], data);
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if ((data & 0x80) == 0) R->Register[r] = (R->Register[r] & 0x3f0) | (data & 0x0f);
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n = R->Register[6];
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/* N/512,N/1024,N/2048,Tone #3 output */
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R->Period[3] = ((n&3) == 3) ? 2 * R->Period[2] : (1 << (5+(n&3)));
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/* Reset noise shifter */
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R->RNG = R->FeedbackMask;
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R->Output[3] = R->RNG & 1;
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}
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@ -225,34 +228,40 @@ static STREAM_UPDATE( SN76496Update )
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sn76496_state *R = (sn76496_state *)param;
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stream_sample_t *lbuffer = outputs[0];
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stream_sample_t *rbuffer = (R->Stereo)?outputs[1]:NULL;
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INT16 out = 0;
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INT16 out2 = 0;
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while (samples > 0)
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{
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// clock chip once
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INT16 out = 0;
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INT16 out2 = 0;
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/* decrement Cycles to READY by one */
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if (R->CyclestoREADY >0) R->CyclestoREADY--;
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// handle channels 0,1,2
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for (i = 0;i < 3;i++)
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// clock chip once
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if (R->CurrentClock > 0) // not ready for new divided clock
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{
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R->Count[i]--;
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if (R->Count[i] < 0)
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{
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R->Output[i] ^= 1;
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R->Count[i] = R->Period[i];
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}
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R->CurrentClock--;
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}
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// handle channel 3
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R->Count[3]--;
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if (R->Count[3] <= 0)
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else // ready for new divided clock, make a new sample
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{
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if (NOISEMODE == 1) /* White Noise Mode */
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R->CurrentClock = R->ClockDivider-1;
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/* decrement Cycles to READY by one */
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if (R->CyclestoREADY >0) R->CyclestoREADY--;
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// handle channels 0,1,2
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for (i = 0;i < 3;i++)
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{
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if ((((R->RNG & R->WhitenoiseTaps) != R->WhitenoiseTaps) && ((R->RNG & R->WhitenoiseTaps) != 0)) ^ R->FeedbackInvert ) /* XOR or XNOR */
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R->Count[i]--;
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if (R->Count[i] < 0)
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{
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R->Output[i] ^= 1;
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R->Count[i] = R->Period[i];
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}
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}
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// handle channel 3
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R->Count[3]--;
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if (R->Count[3] <= 0)
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{
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// if noisemode is 1, both taps are enabled
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// if noisemode is 0, the lower tap, whitenoisetap2, is held at 1 or 0 depending on whether FeedbackInvert is set or clear
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if (((R->RNG & R->WhitenoiseTap1)?1:0) ^ (((((R->RNG & R->WhitenoiseTap2)?0:1))*(NOISEMODE))^R->FeedbackInvert) ^ R->FeedbackInvert )
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{
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R->RNG >>= 1;
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R->RNG |= R->FeedbackMask;
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@ -261,28 +270,13 @@ static STREAM_UPDATE( SN76496Update )
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{
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R->RNG >>= 1;
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}
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R->Output[3] = R->RNG & 1;
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R->Count[3] = R->Period[3];
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}
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else /* Periodic noise mode */
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{
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if (R->RNG & 1)
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{
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R->RNG >>= 1;
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R->RNG |= R->FeedbackMask;
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}
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else
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{
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R->RNG >>= 1;
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}
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}
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R->Output[3] = R->RNG & 1;
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R->Count[3] = R->Period[3];
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}
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/* //bipolar output, doesn't seem to work right with sonic 2 on gamegear at least
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out = (R->Output[0]?R->Volume[0]:(0-R->Volume[0]))
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+(R->Output[1]?R->Volume[1]:(0-R->Volume[1]))
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+(R->Output[2]?R->Volume[2]:(0-R->Volume[2]))
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+(R->Output[3]?R->Volume[3]:(0-R->Volume[3]));
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*/
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if (R->Stereo)
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{
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out = (((R->StereoMask&0x10)&&R->Output[0])?R->Volume[0]:0)
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@ -342,7 +336,7 @@ static void SN76496_set_gain(sn76496_state *R,int gain)
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static int SN76496_init(running_device *device, sn76496_state *R, int stereo)
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{
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int sample_rate = device->clock/16;
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int sample_rate = device->clock/2;
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int i;
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R->Channel = stream_create(device,0,(stereo?2:1),sample_rate,R,SN76496Update);
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@ -361,13 +355,15 @@ static int SN76496_init(running_device *device, sn76496_state *R, int stereo)
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R->Output[i] = R->Period[i] = R->Count[i] = 0;
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}
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/* Default is SN76489 non-A */
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R->FeedbackMask = 0x4000; /* mask for feedback */
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R->WhitenoiseTaps = 0x03; /* mask for white noise taps */
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R->FeedbackInvert = 0; /* feedback invert flag */
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R->CyclestoREADY = 1; /* assume ready is not active immediately on init. is this correct?*/
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/* Default is SN76489A */
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R->ClockDivider = 8;
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R->FeedbackMask = 0x10000; /* mask for feedback */
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R->WhitenoiseTap1 = 0x04; /* mask for white noise tap 1*/
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R->WhitenoiseTap2 = 0x08; /* mask for white noise tap 2*/
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R->FeedbackInvert = 1; /* feedback invert flag */
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R->Negate = 0; /* channels are not negated */
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R->Stereo = stereo; /* depends on init */
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R->CyclestoREADY = 1; /* assume ready is not active immediately on init. is this correct?*/
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R->StereoMask = 0xFF; /* all channels enabled */
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R->RNG = R->FeedbackMask;
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@ -377,7 +373,7 @@ static int SN76496_init(running_device *device, sn76496_state *R, int stereo)
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}
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static void generic_start(running_device *device, int feedbackmask, int noisetaps, int feedbackinvert, int negate, int stereo)
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static void generic_start(running_device *device, int feedbackmask, int noisetap1, int noisetap2, int feedbackinvert, int negate, int stereo, int clockdivider)
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{
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sn76496_state *chip = get_safe_token(device);
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@ -386,18 +382,24 @@ static void generic_start(running_device *device, int feedbackmask, int noisetap
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SN76496_set_gain(chip, 0);
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chip->FeedbackMask = feedbackmask;
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chip->WhitenoiseTaps = noisetaps;
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chip->WhitenoiseTap1 = noisetap1;
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chip->WhitenoiseTap2 = noisetap2;
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chip->FeedbackInvert = feedbackinvert;
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chip->Negate = negate;
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chip->Stereo = stereo;
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chip->ClockDivider = clockdivider;
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chip->CurrentClock = clockdivider-1;
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state_save_register_device_item_array(device, 0, chip->VolTable);
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state_save_register_device_item_array(device, 0, chip->Register);
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state_save_register_device_item(device, 0, chip->LastRegister);
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state_save_register_device_item_array(device, 0, chip->Volume);
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state_save_register_device_item(device, 0, chip->RNG);
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state_save_register_device_item(device, 0, chip->ClockDivider);
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state_save_register_device_item(device, 0, chip->CurrentClock);
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state_save_register_device_item(device, 0, chip->FeedbackMask);
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state_save_register_device_item(device, 0, chip->WhitenoiseTaps);
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state_save_register_device_item(device, 0, chip->WhitenoiseTap1);
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state_save_register_device_item(device, 0, chip->WhitenoiseTap2);
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state_save_register_device_item(device, 0, chip->FeedbackInvert);
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state_save_register_device_item(device, 0, chip->Negate);
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state_save_register_device_item(device, 0, chip->Stereo);
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@ -408,46 +410,46 @@ static void generic_start(running_device *device, int feedbackmask, int noisetap
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state_save_register_device_item(device, 0, chip->CyclestoREADY);
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}
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// function parameters: device, feedback destination tap, feedback source taps, xor(false)/xnor(true), normal(false)/invert(true), mono(false)/stereo(true)
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// function parameters: device, feedback destination tap, feedback source taps, xor(false)/xnor(true), normal(false)/invert(true), mono(false)/stereo(true), clock divider factor
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static DEVICE_START( sn76489 )
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{
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generic_start(device, 0x4000, 0x03, FALSE, FALSE, FALSE); // todo: verify; assumed to be the same as sn94624
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generic_start(device, 0x10000, 0x04, 0x08, FALSE, FALSE, FALSE, 8); // SN76489 not verified yet. todo: verify;
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}
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static DEVICE_START( sn76489a )
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{
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generic_start(device, 0x4000, 0x03, TRUE, FALSE, FALSE); // verified by plgdavid
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generic_start(device, 0x10000, 0x04, 0x08, TRUE, FALSE, FALSE, 8); // SN76489A: whitenoise verified, phase verified, periodic 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, 0x4000, 0x03, TRUE, FALSE, FALSE); // todo: verify; assumed to be the same as sn76489a
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generic_start(device, 0x10000, 0x04, 0x08, TRUE, FALSE, FALSE, 1); // SN76494 not verified, (according to datasheet: same as sn76489a but without the /8 divider)
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}
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static DEVICE_START( sn76496 )
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{
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generic_start(device, 0x4000, 0x03, TRUE, FALSE, FALSE); // todo: verify; assumed to be the same as sn76489a
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generic_start(device, 0x10000, 0x04, 0x08, TRUE, FALSE, FALSE, 8); // SN76496 not verified; 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, FALSE, FALSE); // verified by plgdavid
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generic_start(device, 0x4000, 0x01, 0x02, FALSE, TRUE, FALSE, 1); // SN94624 whitenoise verified, phase verified, period verified; 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, 0x8000, 0x22, FALSE, FALSE, FALSE); // todo: verify; from smspower wiki
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generic_start(device, 0x8000, 0x02, 0x20, FALSE, FALSE, FALSE, 8); // NCR7496 not verified; info 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, FALSE, TRUE, TRUE); // Verified by Justin Kerk
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generic_start(device, 0x8000, 0x01, 0x08, FALSE, TRUE, TRUE, 8); // Verified by Justin Kerk
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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, FALSE, TRUE, FALSE); // todo: verify; from smspower wiki, assumed to have same invert as gamegear
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generic_start(device, 0x8000, 0x01, 0x08, FALSE, TRUE, FALSE, 8); // todo: verify; from smspower wiki, assumed to have same invert as gamegear
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}
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