$D012 values on C64

From: Michał Pleban <*lists_at_michau.name*> Date: Tue, 18 Jun 2013 18:26:34 +0200 Message-ID: <51C08A3A.2050203@michau.name> · lists_at_michau.name

Hello!

I am writing the software for my MultiKernal Flash device for C64. I
found that during writing to the Flash chip I need to disable chip
reads, because otherwise they mess up with magic write sequences.

But then VIC-II cannot read character ROM, which results in garbled
screen display. Therefore I would like to write to the Flash chip only
when character ROM is not needed - i.e. when the lower or upper border
is drawn. For this, I need to consult the $D012 register.

However, I have only a PAL machine and I don't know how the values look
like on a NTSC machine. I would assume that they both start at 0 and the
border starts/ends at the same positions as with PAL, only possibly the
total number of lines is different - is that a correct assumption?

Regards,
Michau.

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