> All mappers use ports FC-FF. More than one mapper can be present in a
> system. When writing, no problem, all mappers accept the same value. When
> reading, there is a problem when two mappers want to return different
> values (for example because they are not equally large).
>
No problems here. The "smaller" mapper actualy doesn't return the upper bits.
The "1"s there are caused by +5v pull-up of data bus. If we connect a larger
mapper the lower bits will be identical and the data bus 1s in the higher bits
will be
replaced by the value returned from the larger mapper. This works OK, this is the
method I used to extend memory on my Yamaha.
In fact I don't mind using different kinds of memory management routines. but...
This is acceptable for application programs - and not always so for sytem
programs.
And then, repairing hardware bugs with software is anything but the best method.
Probably producers of memory extensions will finaly modify their hardware to make
mappers readable? (and, better, 8-bit).
****
MSX Mailinglist. To unsubscribe, send an email to [EMAIL PROTECTED] and put
in the body (not subject) "unsubscribe msx [EMAIL PROTECTED]" (without the
quotes :-) Problems? contact [EMAIL PROTECTED] (www.stack.nl/~wiebe/mailinglist/)
****
