> >> 1 SP ? Sprite (0=On, 1=Off)
> >
> >The name is SPD, not SP. With it you can disable the sprites, which
> >drastically spees up the VDP (that's why the name is SPeeD).
Hmm, I don't think SPD comes from SPeeD, more something like SPrite Disable.
> >> 4 CB colour Bus direction (0=Output, 1=Input)
> >
> >This one can also have 1 value, otherwise the VDP won't work (it might even
> >blow up!).
>
> OOPS! Same seems to go for PSG register 7. 10xxxxxx or BANG!
Yes, look in The MSX Red Book (ftp://ftp.funet.fi/pub/msx/txt/tech/tredbook.arj
)
Quote:
Register 7
This register enables or disables the Tone Generator and
Noise Generator for each of the three channels: 0=Enable
1=Disable. It also controls the direction of interface ports A
and B, to which the joysticks and cassette are attached:
0=Input, 1=Output. Register 7 must always contain 10xxxxxx or
possible damage could result to the PSG, there are active
devices connected to its I/O pins. The BASIC "SOUND" statement
will force these bits to the correct value for Register 7 but
there is no protection at the machine code level.
End Quote.
Wrong use of this register caused several programs to fail on the Sony
HB-G900P. It didn't blow up it's PSG, but the joystick routines didn't work.
Examples are The Shrines of Enigma (Element/Sunrise), The Futuredisk (now
corrected, thanks Jeroen!) and Bomberman (Paragon, now corrected, thanks
Antal!). In the section Noorder Baken of the former Dutch magazine MCCM a
routine was once published with the wrong PSG settings, therefore some
programs contained this error. So beware! And indeed: in the worst case the
chip can be blown up due to short-circuit.
By the way: something similar is the case if I try to run that crack of
Advanced Dungeons & Dragons on my Sony 900. It hangs the MSX, and after a
reset it won't start again...! (as if a cartridge is badly placed in the
slot). AFter turning it off for a while it will start again... (the MSX I
mean, the game doesn't work at all... Well, it's not such a good game anyway!)
> The first time I laid my hands on an MSX I POKED the PSG register 7
> directly... with 00xxxxxx!!! My 8250 sounds real bad when doing phaser
> effects, so I presume perhaps I blowed something with that POKE?!?!?
Could be. But the software mentioned above didn't cause any damage, as far as
I know.
Note that I posted a mail about this I guess more than a year ago... ;-)
Grtjs, Manuel ((m)ICQ UIN 41947405)
PS: MSX 4 EVER! (Questions? See: http://www.faq.msxnet.org/)
PPS: Visit my homepage at http://www.sci.kun.nl/marie/home/manuelbi/
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