MMC1 SXROM 32kB WRAM Banking
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MMC1 SXROM 32kB WRAM Banking
How does 32 kB WRAM work in MMC1 SXROM? It's about access to the whole 32kB - do you have to control four banks of 8kb each ($ 6000-7FFF), or maybe switching $ 8000-FFFF between ROM and RAM?
Re: MMC1 SXROM 32kB WRAM Banking
This.sdm wrote:do you have to control four banks of 8kb each ($ 6000-7FFF)
Is the wiki page on MMC1 unclear? If so, how can we improve it?
Re: MMC1 SXROM 32kB WRAM Banking
In addition, not everyone knows English perfectly, which in the case of technical matters is also more difficult.lidnariq wrote: Is the wiki page on MMC1 unclear? If so, how can we improve it?
I would like to make sure - that is 32kB are four banks of 8kB each, switched by bits 2-3 of the C000-DFFF register?
00 - first bank
01 - second
10 - third
11 - last
example:
lda 00001100
sta C000
= select last 8kb bank of 32kB SXROM WRAM?
??
Last edited by sdm on Wed Jun 26, 2019 7:12 am, edited 1 time in total.
Re: MMC1 SXROM 32kB WRAM Banking
Usually, if you're using large ROM or large SRAM with MMC1 (SOROM, SUROM, SXROM), you set 8K CHR mode in $8000 and write the bank number to $A000. You also write the bank number serially, one bit at a time for five bits.
Re: MMC1 SXROM 32kB WRAM Banking
switch to last 8kb bank of 32kB SXROM WRAM:
lda #%00001100
sta $A000
lsr a
sta $A000
lsr a
sta $A000
lsr a
sta $A000
lsr a
sta $A000
correct?
lda #%00001100
sta $A000
lsr a
sta $A000
lsr a
sta $A000
lsr a
sta $A000
lsr a
sta $A000
correct?
Re: MMC1 SXROM 32kB WRAM Banking
Correct, though this also changes to the first 256 KiB bank of a PRG ROM larger than 256 KiB.