mapped roms and page 0

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By zPasi

Champion (440)

Аватар пользователя zPasi

28-02-2019, 16:03

ARTRAG wrote:

If the A14 line is not connected you should be able to see always the same thing in 0000-3FFF and 4000-7FFF
This doesn't happen always

In which case it doesn't?

By NYYRIKKI

Enlighted (5358)

Аватар пользователя NYYRIKKI

28-02-2019, 16:13

zPasi wrote:
ARTRAG wrote:

If the A14 line is not connected you should be able to see always the same thing in 0000-3FFF and 4000-7FFF
This doesn't happen always

In which case it doesn't?

As I explained already, this mirroring effect is usually masked by usage of /CS12 pin.

By zPasi

Champion (440)

Аватар пользователя zPasi

28-02-2019, 17:33

NYYRIKKI wrote:
zPasi wrote:
ARTRAG wrote:

If the A14 line is not connected you should be able to see always the same thing in 0000-3FFF and 4000-7FFF
This doesn't happen always

In which case it doesn't?

As I explained already, this mirroring effect is usually masked by usage of /CS12 pin.

I see. If the cart uses that, there will be no mirroring. Only designs using just /SLTSL produce mirroring.

By ARTRAG

Enlighted (6236)

Аватар пользователя ARTRAG

28-02-2019, 20:19

In addition, why what you get with the two Konami mappers differ?
One is mirroring the lower page, the other the upper page...

By zPasi

Champion (440)

Аватар пользователя zPasi

28-02-2019, 21:50

ARTRAG wrote:

In addition, why what you get with the two Konami mappers differ?
One is mirroring the lower page, the other the upper page...

Oh, you mean like this one?

Quote:

Now tests with real Salamander cartridge (SCC mapper):
A relevant difference:
(8000h-Bfffh) mirrored in (0000h-3fffh)

Looks like in that one, A14 is connected and A15 is not. If I'm correct, 4000-7fff is also mirrored in c000-ffff.

By gdx

Prophet (2977)

Аватар пользователя gdx

01-03-2019, 00:43

With 32k ROM (0000-7FFF) when address line A15 is ignored the 32k is mirrored on upper 32k (8000-FFFF) but on MSX 32k Roms or Megarom konami/ASCII that use signal /S12 the addresses are shifted to 4000h so 4000-7FFF adresses are mirrored to C000-FFFF and 8000-BFFF to 0000-7FFF.

These mirrors can be useful for making a Rom loader for Megaflashrom or Megasram. A few 32K roms are located on 0000-7FFF or 8000-FFFF. I had thought of it for FL.COM but I have not taken yet the time to do it.

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