Ascii 8kb mapper, confused

By lintweaker

Champion (288)

lintweaker's picture

24-06-2020, 11:48

I am busy designing a new disk interface with support for a ASCII 8kb mapper so it can use Nextor.
Looking at the schematic it seems to use A12 and A11 to read the 74670 register and select the required page in ROM.
To me this not make any sense, should this not be A15 and A13?

Schematic see first page:
https://www.hvandeven.com/msx/ascii-konami-scc-mapper.pdf

EDIT: Scratch that, I was really confused, got it now! :)

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By Fabf

Master (243)

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24-06-2020, 12:39

This design will not work as pages will not be in the right order.
Same issue with SCC mapper.
Only Konami mapper will work well with flashrom.
Sorry I don't know how to fix this.

By lintweaker

Champion (288)

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24-06-2020, 12:56

Fabf wrote:

This design will not work as pages will not be in the right order.
Same issue with SCC mapper.
Only Konami mapper will work well with flashrom.
Sorry I don't know how to fix this.

Do you mean the design will work a read only mapper but there are issues with flashing?
Enabling flash erase/write mode will interfere with the mapper (and vice versa).

By Fabf

Master (243)

Fabf's picture

24-06-2020, 16:28

You can flash and reset the computer, the ROM will start well.
But if you shut down the computer the ROM will not start.

By gdx

Prophet (3683)

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24-06-2020, 17:20

Except if the pages are defined by software from the page 0. Nextor do it.

By lintweaker

Champion (288)

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24-06-2020, 20:33

Okay, the design has a CPLD on board which can set the appropriate pages on reset. Otherwise I'll make something to be able disable the mapper function for flashing.

By Fabf

Master (243)

Fabf's picture

24-06-2020, 21:25

It should works this way.