How do you initialize the mapper from basic? (sorry guys, Im new in MSX)
The trick is to set pages in order, the most tricky ones last:
OUT(252),3
OUT(253),2
OUT(254),1
A BASIC program may switch itself away here, but hand-typed no problem.
OUT(255),0
@ This point an MSX1 may hang. But who cares, the OUT is done. Just hit [RESET] button here to reboot machine with the mapper properly set. Hardware reset is fine - just don't power off or you'll have to re-do the above. Or, if machine doesn't hang & you prefer typing:
An MSX1 can't hang with this instruction (if enter just after a boot).
RetroTechie wrote:
But who cares, the OUT is done. Just hit [RESET] button here to reboot machine with the mapper properly set. Hardware reset is fine - just don't power off or you'll have to re-do the above.
This is only valid with the classic Memory Mappers that does not take into account the reset signal.
Fortunately a majority of MSX1 have no reset button but I suggest anyway to avoid these Mappers.
This is only valid with the classic Memory Mappers that does not take into account the reset signal.
Fortunately a majority of MSX1 have no reset button but I suggest anyway to avoid these Mappers.
IMHO, if the mapper is natively supported by the HW, it must be initialized by the built-in BIOS. For example, Yamaha CX5MII/128 is an MSX1 computer with the memory mapped 128K of RAM. Its memory mapper is initialized by the BIOS correctly at the bootstrap. And the mapper init is done even not by the Yamaha CX5M BIOS extension, but the MAIN MSX1 BIOS.
Are there any other MSX1 computers with the memory mapped RAM? It would be interesting to analyze if there is a common solution to the registers initialization
An MSX1 can't hang with this instruction (if enter just after a boot).
Yes, after a cold boot that register should be zero anyway, so OUT 255,0 doesn't do much.
Quote:
This is only valid with the classic Memory Mappers that does not take into account the reset signal.
Fortunately a majority of MSX1 have no reset button but I suggest anyway to avoid these Mappers.
I haven't seen a DIY mapper that properly initialises itself on reset. It's not easy to initialise 74xx670 registers without a processor. With CPLD it's not a problem, but investing time and money learning that stuff for a one-time DIY project isn't very practical IMO.
Since I have all the parts, I think I'll give it a go and see. I the worst of the cases I can use it with my MSX2 machines.
That particular mapper works fine, but it has no readback on the mapper register (returns 0xFF on reads). European software will fail running with it. But it should work perfectly fine with Japanese software (including DOS2).
