z80 still available for sound?

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slobu
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z80 still available for sound?

Post by slobu » Wed Nov 07, 2012 12:52 pm

So, I'm using Shirus TFM Music Maker for 6 channel FM music and the z80 for 8-bit mono wave samples.

When I burn an ISO and run it on my X'Eye the z80 driver actually plays back sound! It's unrecognizable from the original sample but it's there!

Is this a quirk of the X'Eye? If I can even get screeches does this mean it may be possible to modulate the samples to play correctly?
Last edited by slobu on Wed Nov 07, 2012 3:10 pm, edited 1 time in total.

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TmEE co.(TM)
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Post by TmEE co.(TM) » Wed Nov 07, 2012 2:01 pm

YM is monopolised by both sides... but ony one side can do it, so you end up with a giant mess.
Interactions with the YM mist be coordinated on both Z80 and 68K side, both sides cannot do an access at the same time without messing up everything.
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Chilly Willy
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Post by Chilly Willy » Wed Nov 07, 2012 2:46 pm

Playing samples on CD Z80 software... lemme guess, you're playing them out of word ram...

Sega's tech bulletins say the Z80 cannot read CD word ram. In fact, the only memory the Z80 can read in CD software is its own sram. The Z80 cannot read the MD work ram, so the only way the Z80 could get samples to play is for the program to use the 68000 to copy them into sram for the Z80.

This lack of any memory for the Z80 to use other than the 8KB of sram in CD software is one of the biggest issues CD programs face in trying to use the Z80. It's part of why the CD has a PCM chip in it - you're expected to use that instead of the Z80/FM/PSG.

slobu
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Post by slobu » Wed Nov 07, 2012 3:13 pm

I really, really appreciate the knowledgeable answers!

I figured it was a longshot. I guess if I wanted to make a game easily transitioned between CD and cart is to just allocate some of the FM channels for sound effects. Maybe 4 for music and 2 for sound effects.

Chilly Willy
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Post by Chilly Willy » Wed Nov 07, 2012 4:20 pm

Well, you could play PCM on the Z80 for cart, and on the PCM chip for CD. FM can stay on the FM, but you'd need to be conscious of that 8KB limit for FM when running from CD.

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