Fixed AY-3-8910 sound for Champion Base Ball Part-2 (Japan)

[MASHinfo]

Fixed AY-3-8910 sound. You can hear now the INSERT COIN tune and the ingame music.

[MASHinfo]

Here is a snap to compare the DASM of Champion Base Ball Part-2 (set 1) and clone Champion Base Ball Part-2 (Japan)

http://mameinfo.mameworld.info/pics/DASM_champbb2-champbb2j.png

[cuavas]

This change makes no sense - you couldn't get that effect with simple address decoding logic. It's more likely missing mirroring. Please try to find schematics and work from there.

[MASHinfo]

The AY-3-8910 sound is completely missing in clone Champion Base Ball Part-2 (Japan).
Only the DAC sound is working. The parent set Champion Base Ball Part-2 (set 1) uses
the address 0x7000 and 0x7001, while the clone uses 0x7001 + 0x7002 to write commands
to the AY-3-8910 chip. There is no write mirroring - compare both programs.

[rb6502]

On the contrary, that sounds like the AY is mirrored throughout the 7000-77FF range and will respond to any of those addresses. Only schematics can tell for sure, but the software behavior certainly suggests that.

[ghost]

could also be they fudged it on the board as security to stop unofficial upgrades tho

[angelosa]

To me it sounds plausible that they reversed data / address ports for this specific revision.
And of course it must start at 0x7000 - 0x7001 with mirroring.

[ajrhacker]

Address decoding logic for the AY-3-8910 tends to be bizarre and intricate due to the unconventional bus signals the device was designed around. I've even seen schematics where the low address lines are encoded through a SN74LS148 (with an inverter stage following that).

Unfortunately, official schematics aren't always a perfect guide even when they're available to those who understand them. Important details can be rendered illegible through photocopying, outright absent to begin with (as in the case of Arkanoid), or obfuscated through apparent errors (as seems to be the case with this game). Often only one revision of the PCB is documented when multiple software-incompatible ones were produced (which also appears to be the case here).

The Champion Baseball Part 2 schematics show details of the AY-3-8910 address decoding circuit which are not entirely reconcilable with the driver. The (half of a) 74LS139 that produces the BDIR and BC1 signals is enabled by the strobe decoding the 7000-7FFF range. Its A and B address inputs (those on the AY-3-8910 are tied to the active state) are probably A0 and A1, though "A12" is inexplicably given for the latter. Of the four decoder outputs, only two activate the AY-3-8910, and A0 is used to decide whether the address register or data register is to be written to (read access is precluded). The appropriate mirroring for the address map is therefore likely 0xffc.

...actually, looking at the Champion Baseball schematic, that game's address decoding has one strobe for the entire 6000-7FFF range. So A12 probably is the intended B input for the 74LS139 after all, and the mirroring should fill the 7000-7FFF range throughout.

[cuavas]

Should be fixed in 3f024b8 if this is correct.