MSX FM-music fans, look here!

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Van o.geerdink

Hero (585)

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08-04-2016, 13:45

Msx audio automaticly switches to other port if there are 2??

Van Grauw

Ascended (10156)

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08-04-2016, 14:07

No, you need a hardware modification for the 2nd MSX-AUDIO.

Van tvalenca

Paladin (747)

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08-04-2016, 21:28

NYYRIKKI wrote:

Here are the FM-PAC addresses: (Greetz to BiFi)

	7FF4h: write YM-2413 register port (write only)
	7FF5h: write YM-2413 data port (write only)
	7FF6h: activate OPLL (read/write)
	7FF7h: ROM page (read/write)

Oh, that's very interesting... so the OPLL is also a memory mapped device! Replicating this scheme anyone could install mutiple OPLLs on a single MSX! This is something I'll surely will do when I have time for new projects!

Thanks on the info!

Van NYYRIKKI

Enlighted (5889)

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08-04-2016, 22:48

tvalenca wrote:

so the OPLL is also a memory mapped device! Replicating this scheme anyone could install mutiple OPLLs on a single MSX! This is something I'll surely will do when I have time for new projects!

Indeed... This information has been out there for years and years, yet I've not managed to see even ONE program to actually use it for anything. This is one of the reasons why I wanted to try now if it even works or not... And I can conclude that: Yes, it works, no one just cares. Smile I think it is because there are so many clones / embedded MSX-MUSICs out there and they do not support this secondary method.

Van tvalenca

Paladin (747)

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08-04-2016, 23:48

NYYRIKKI wrote:
tvalenca wrote:

so the OPLL is also a memory mapped device! Replicating this scheme anyone could install mutiple OPLLs on a single MSX! This is something I'll surely will do when I have time for new projects!

Indeed... This information has been out there for years and years, yet I've not managed to see even ONE program to actually use it for anything. This is one of the reasons why I wanted to try now if it even works or not... And I can conclude that: Yes, it works, no one just cares. Smile I think it is because there are so many clones / embedded MSX-MUSICs out there and they do not support this secondary method.

NYYRIKKI, can you test something?

IIRC, you have a Turbo R GT, right? This Turbo R is well known for blocking requests for internal peripherals to reach the external bus (cartridges). So, a I/O Bus write for the OPLL I/O ports never reach an external OPLL cartridge. Am I right? (Or only the bus reads are blocked?)

BUT, what happens if you insert the original FM-PAC on Turbo-R GT slot? do it work with any software? or Just with software that send data through those memory addresses?

Van NYYRIKKI

Enlighted (5889)

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09-04-2016, 01:17

tvalenca wrote:

NYYRIKKI, can you test something?

IIRC, you have a Turbo R GT, right? This Turbo R is well known for blocking requests for internal peripherals to reach the external bus (cartridges). So, a I/O Bus write for the OPLL I/O ports never reach an external OPLL cartridge. Am I right? (Or only the bus reads are blocked?)

BUT, what happens if you insert the original FM-PAC on Turbo-R GT slot? do it work with any software? or Just with software that send data through those memory addresses?

No, you are way off the course... As I said earlier, FM-PAC checks if you have internal MSX-MUSIC (as found in MSX tR for example) and only in case it doesn't found one, it turns on the I/O ports. This is done in order to avoid conflicting with the existing hardware. If you force the I/O ports active the same data get sent to both MSX-MUSICs and this messes up the volume balance between PSG & MSX-MUSIC. PAC functionality & memory mapped I/O is available no matter if you have activated the I/O ports or not. Bus buffering does not have anything to do with this.

External software (ML programs on disk) usually don't check for double MSX-MUSIC scenario. If they find FM-PAC they just activate the I/O ports. How ever because in MSX tR they first find internal MSX-MUSIC from slot 0-2 they don't advance ever to FM-PAC slot and this is why the conflict does not occur with disk games either. In perfect world the ML program would call the MSX-MUSIC INIT-routine that would take care of possible conflict situations regardless of what is the slot order, but practically this most used solution that I described works already well.

Van Meits

Scribe (6458)

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09-04-2016, 01:10

This does not only count for turbo R GT. The ST and the 2+ machins switch off the original panasonic FM-PAC as well in regular setups. The clones don't "suffer" this and will always play.

Van Grauw

Ascended (10156)

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09-04-2016, 01:24

Afaik the Panasonic MSX2+ and turboR computers do not block MSX-MUSIC I/O ports.

Why an external Panasoft FM-PAC doesn’t sound is due to this:

	7FF6h: activate OPLL (read/write)

Because the internal MSX-MUSIC is found first, the external FM-PAC is never activated and remains off (default startup state). Clones don’t have the on/off switch, so they are always enabled.

Van NYYRIKKI

Enlighted (5889)

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09-04-2016, 01:42

Meits wrote:

This does not only count for turbo R GT. The ST and the 2+ machins switch off the original panasonic FM-PAC as well in regular setups. The clones don't "suffer" this and will always play.

This is where we have our different perspective to the issue.. You see this feature as a problem while I think it is very good design and makes it possible to use FM-PAC even on MSX tR. Smile

BTW now that we are talking about this issue... Do not write always blindly to #7FF6 if the device is not FM-PAC... In Panasonic 2+ computers this will not switch MSX-MUSIC on but instead it will switch off part of the ROM... I'm pretty sure you don't want to do that, because ie. next BASIC CALL-command will crash the computer. ie. original Moonblaster replayer suffered from this and this is why European software has quite some problems with Panasonic MSX2+ computers. This issue was fixed somewhere beginning of this millennium, but there is still lot of software out there that has this bug.

Van Meits

Scribe (6458)

afbeelding van Meits

09-04-2016, 01:45

I did write "suffer" Wink
For me it was suffering since I dislike the audio quality coming out of the RCA/RGB outlets on an MSX computer due to the VDP noise you get with it for free.

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