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Post by dshadoff on Nov 16, 2019 15:03:18 GMT
A long time ago, it was discovered that the code for unlocking BRAM used a 3-byte write sequence to $1807 ($48, $75, $80), but nobody could figure out why, since just writing $80 seemed to do the trick on everything we could find at the time.
It turns out that the Tennokoe 2 add-on seems to require the 3-byte sequence, as Mooz has just discovered.
Since HuC was originally written with this 1-byte substitution sequence, anything written in HuC (at least up to v3.21), or hand-written based on what was in HuC libraries, may not work with the Tennokoe 2.
I’m trying to quickly find one myself to look inside of it, but Mooz confirmed this only works with the full 3-byte sequence.
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Post by elmer on Nov 16, 2019 23:16:52 GMT
Thanks Dave and Mooz! I'll put a fix into the current HuC ... and also TEOS, since that currently uses the 1-byte sequence, too.
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Post by ccovell on Nov 17, 2019 5:20:56 GMT
A long time ago, it was discovered that the code for unlocking BRAM used a 3-byte write sequence to $1807 ($48, $75, $80), but nobody could figure out why, since just writing $80 seemed to do the trick on everything we could find at the time. It turns out that the Tennokoe 2 add-on seems to require the 3-byte sequence, as Mooz has just discovered. This was discovered many moons ago and discussed on the other PCEFx boards in 2015, a quick search shows.
In other interface-related news, the sequence lda #$AA sta $18C0 lda #$55 sta $18C0 ;Unlocks Super CD-RAM!
Can unlock SCD RAM in bank $68-$7F from a HuCard on a real interface unit, but not on the TerraOnion SSDS3. The SSDS3 will only allow SCD RAM access if you boot from a CD game / System Card.
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TailChao
Gun-headed
I Must Eat Muffin Gear.
Posts: 68
Fave PCE Game Overall: Bonk's Adventure
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Post by TailChao on Nov 17, 2019 15:37:55 GMT
In other interface-related news, the sequence lda #$AA sta $18C0 lda #$55 sta $18C0 ;Unlocks Super CD-RAM! Can unlock SCD RAM in bank $68-$7F from a HuCard on a real interface unit, but not on the TerraOnion SSDS3. The SSDS3 will only allow SCD RAM access if you boot from a CD game / System Card.
That's probably a good thing, so then there's no chance of accidentally enabling the Super CD-RAM and causing bus fights.
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Post by dshadoff on Nov 17, 2019 18:26:51 GMT
A long time ago, it was discovered that the code for unlocking BRAM used a 3-byte write sequence to $1807 ($48, $75, $80), but nobody could figure out why, since just writing $80 seemed to do the trick on everything we could find at the time. It turns out that the Tennokoe 2 add-on seems to require the 3-byte sequence, as Mooz has just discovered. This was discovered many moons ago and discussed on the other PCEFx boards in 2015, a quick search shows. Thanks for pointing this out. I vaguely recall this but it didn’t register at the time that I would need to amend HuC libraries. But now I know.
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