Martial BENOIT wrote:
> At 00:27 26/05/98 +0200, you wrote:
>
> >The problem with the MSX turbo R is that the pull-up resistors in the
> engine (S1990) have a
> >too low resistance, which makes the current that high that even the
> low-bit produced by an
Pull-up inside the engine? Sounds VERY interesting.
> >external large mapper will be pulled up. In theory this can damage both
> the external mapper
> >and the S1990. I don't think that Panasonic will produce a new version of
> the S1990 to solve
> >that problem. I don't think that Panasonic will produce anything anymore
> for MSX. So we will
> >have to live with these problems and work around them with software
> routines! Whether we like
> >it or not :-(
>
> I use a self made upgrade using a 1MB SIMM 80ns (30 pins PC DRAM) and some
> 74HCxx chips to enable read and write to the 'missing' 3 upper bit of the
> mapper registers, and I haven't destroy my S1990 until now.
And this seems to prove my theory about S1990 actualy NOT outputting higher
mapperbits.
> It seem that you have the some data about the internal structure of the S1990.
>
> May I ask you if you could tell me what is the value of the pull up
> resistors for the 3 upper bits of the mapper registers?
>
Did anyone actualy TRY to read external mapper on the Turbo R?
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