] On Tue, 20 Jun 2000, David Heremans wrote:
]
] > Is there some page which could tell me how all the MSX version react on
] > an in a,(#FF). I know it shouldn't be done but I'm trying to change a
] > program...
]
] In MSX turbo R and some MSX2+ machines, the upper 3 bits will always be 1.
]
] The value read will be the selected segment in the largest mapper in the
] system.
Unfortunately this is not the case on the MSX turbo R when you insert an
external mapper with a size larger then 512kB. The MSX turbo R has
low-impedance pull-up registers for the 3-upper bits. They pull the line up
stronger then the average external mapper can pull the line down. Hence, the
3-upper bits will always be 1. Even if the external mapper tries to pull one
of those bits down to 0.
Kind regards,
Alex Wulms
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