adding LFO to some alpha denshi games' music #5995
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maybe not a proper way.
maybe not a proper way.
| uint8_t MSM5232frq; | ||
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| static const int8_t equitesLFOwaveform[9] = {-128, -98, -43, 42, 97, 127, 77, -13, -83}; // sine like | ||
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The actual way the LFO circuit's rate and depth works is with a 32-byte, 8-bit PROM (only the low 5 bits of output are used) whose current address is initially zero, and is incremented on every write to 0xC0FC, see the code at equites.cpp line 428.
The PROM in question is bprom.3h:
ROM_REGION( 0x0020, "prom", 0 )
ROM_LOAD( "bprom.3h", 0x00000, 0x020, CRC(33b98466) SHA1(017c73cf8c17dc5047c89316ae5b45f8d22092e8) )
This produces a 32 sample long, 5 bit deep sine wave, which uses an R2R DAC and complicated bit of analog circuitry to vary the clock rate of the msm5232; there is also a trim-pot involved, which probably sets the vibrato 'depth' or perhaps some sort of DC offset, it isn't clear yet.
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The trimpot (labeled FRQ) actually sets the tuning/center frequency of the LFO for the MSM5232 clock, and annoyingly it isn't clear what it is supposed to be set to.
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Based on the initial writeup, the OP isn't going to be able to bring this up to standard. @Lord-Nightmare can you take a look at it since you're familiar-ish with the circuit? |
…e issued, fixes macr2036 (MT #5995), jleagt94, iganin
* pce_cd.cpp: convert to logmacro, fix regression on stop/repeat conditions, workaround MT#07972 * Delete unnecessary stub files from the other branch * hash/pcecd.xml: QA notes * nec/pce_cd.cpp: fix MT#07972 for good * hash/pcecd.xml: update QA * hash/pcecd.xml, nec/pce_cd.cpp: update QA * nec/pce_cd.cpp: make pregap to have a minimum of 2 seconds, fixes redbook offset * sound/cdda.cpp: add an actual write callback for audio playback end event * nec/pce_cd.cpp: implement CDDA audio end event, fixes redbook repeat with emeraldd * hash/pcecd.xml: update QA * nec/pce_cd.cpp: do not send an irq when start/end redbook commands are issued, fixes macr2036 (MT #5995), jleagt94, iganin * hash/pcecd.xml: QA heavy hitters * hash/pcecd.xml: QA * nec/pce_cd.cpp: unbreak snatcher, unbreak audio CD player * nec/pce_cd.cpp: document crazyhos btanb * nec/pce_cd.cpp: make BRAM to init to a standard scdsys format data * hash/pcecd.xml: acknowledge games using Save-Kun peripheral * nec/pce_cd.cpp: fix cdda get_channel_volume index overflow * sound/cdda.cpp: fix longstanding regression with get_channel_volume, rename it to get_channel_sample * nec/pce_cd.cpp: QA fader * nec/pce_cd.cpp: cancel redbook when audio start + play mode = 0 is issued, fixes ppersia sound when picking up sword * hash/pcecd.xml: finalize QA * nec/pce_cd.cpp: misc cleanups * hash/pcecd.xml: fix neklegbb description tag * hash/pcecd.xml: faussete/traveler description fixes
I am not familiar with C/C+, emulation technologies, the structure of MAME's codes, electronic circuits, but could not keep patience waiting for it to be implemented in the future. maybe this implementation is not good, but it is all I can.