F4/FMPAC Light Combo Board project

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By Alexey

Guardian (2535)

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05-03-2016, 23:20

It's only an error in the silkscreen, not in the schematics. You just need to solder one chip in place of another. Solder 74LS74 chip onto the place marked as 74LS125 and solder 74LS125 chip onto the place marked as 74LS74. This is true only for the board that has those chips on the bottom side.

By Alexey

Guardian (2535)

Alexey's picture

19-03-2016, 00:58

It appears that the Yamaha SFG module's bios can't be started with "call music" if the FMPAC board is installed with its own bios. It happens because the original FMPAC bios passes the control back to the system incorrectly. I patched the FMPAC bios so that the SFG module's bios could be called even if FMPAC board is installed. You can download the patched bios from here:

http://zx-pk.ru/attachment.php?attachmentid=56508&d=1458345222

By mars2000you

Enlighted (5525)

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19-03-2016, 01:10

If the SFG module is used on a machine with internal or external MSX-MUSIC chip, you need to enter POKE &HFCD2, 0 : CALL MUSIC or POKE &HFCD2, 0 : _ MUSIC.

No need to patch MSX-MUSIC rom. Just use CALL MUSIC for MSX-MUSIC and POKE &HFCD2, 0 : _ MUSIC for SFG.

By Alexey

Guardian (2535)

Alexey's picture

19-03-2016, 01:31

The poke doesn't seem to work in the emulator with our 16kb internal bios that is used with the FMPAC board. The bios loses the offset to the calling string when it passes control to the system, so the other modules have no chance to get the correct string.

By Alexey

Guardian (2535)

Alexey's picture

23-03-2016, 18:13

Note: if you are using the boards with OTP (one-time programmable) 27c128 or 27c256 EPROM, you will need to get a new chip for this patched bios.

By NYYRIKKI

Enlighted (5425)

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24-03-2016, 08:25

No POKEs or patches needed... I've used more easy solution... To use MSX-MUSIC I've used command CALL MUSIC and to start SFG internal software, I've used command CALL MUSICA

I think the reason why CALL MUSIC does not pass control back to system is because it is designed so that you can use internal MSX-MUSIC and FM-PAC together... Unfortunately I've not seen any other use for this combo than using PAC of the FM-PAC in games even if you have MSX-MUSIC built in your machine... So far I've seen 0 software that would use 2xOPLL (BTW here we come back to the APRLOPLL vs. PAC2OPLL issue)

By Alexey

Guardian (2535)

Alexey's picture

24-03-2016, 18:35

The FMPAC bios that we used checks for "call jppac", the external bios checks for "call fmpac". Both calls will not work on the systems with our combo board because the bios version we use there is only 16kb. Using the full bios is possible, but impractical - there's no SRAM on board and the only useful thing that the full bios will be good for is playing demo tunes.

In our case the FMPAC bios sits in slot 31 and SFG bios sits in slot 33. I don't know where the internal FMPAC bios sits on the MSX2+ machines, maybe it's designed to be the last bios to receive the call parameters. The code passes control to the system, but loses the value of HL register that contains call's parameter. This seemed to be some sort of bug to me, so I fixed it. Smile

By mars2000you

Enlighted (5525)

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24-03-2016, 19:14

In MSX2+ and MSXturboR Panasonic machines, MSX-MUSIC chip is in slot 0-2 (but no any MSX-MUSIC in FS-A1FX).

In MSX2+ Sony and Sanyo machines, it's in slot 3-3 (but no any MSX-MUSIC in Sanyo PHC-35J).

By NYYRIKKI

Enlighted (5425)

NYYRIKKI's picture

24-03-2016, 20:33

I don't know if the "problem" you described is intentional or not, but at least by fixing it you disable possibility to use MSX-MUSIC BASIC programs when SFG is installed. Also on FM-PAC & MSX-MUSIC setup that would cause initialization routines to be called two times. That is why I don't want the fixed version. Smile

Ok, the best solution would be changing the start command on SFG as external programs don't use it, but that would require new ROM also.

By Alexey

Guardian (2535)

Alexey's picture

24-03-2016, 20:57

Timo, I am a bit confused now. If both MSX Music and SFG use the same calling parameter (call music) then obviously MSX Music will not work because SFG will start its internal program after this call. The FMPAC does not use "call music" call, it uses "call fmpac" call, so it should not interfere with any other sound hardware. However when it does not allow the calling string to be passed further, this prevents all other hardware in higher slots to be called. Am I missing anything?

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