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by Chilly Willy
Tue Jul 28, 2020 10:11 pm
Forum: Mega/SegaCD
Topic: mcd-verificator (CD core accuracy tests)
Replies: 24
Views: 5430

Re: mcd-verificator (CD core accuracy tests)

@Chilly Willy are you saying that MCD doesn’t put the 68K bus in high impedance when hasn't taken the MD-68K bus? No, I was saying the 32X puts the 68K bus in high impedance to avoid loading down the CD. When the MD 68K tries to access the registers, the CD is supposed to respond. If the 32X didn't...
by Chilly Willy
Tue Jul 28, 2020 12:22 am
Forum: Mega/SegaCD
Topic: mcd-verificator (CD core accuracy tests)
Replies: 24
Views: 5430

Re: mcd-verificator (CD core accuracy tests)

I made some tests with 32x and is seems like 32x does not pass data lines in memory areas related to mega cd, may be it been made to avoid bus conflicts. Makes sense - the IO chip can decode the CD space and tri-state the data bus to make sure an attached CD doesn't have an extra load on the bus to...
by Chilly Willy
Mon Jul 27, 2020 1:28 pm
Forum: Demos
Topic: Game Raccoon - Open Hardware/Software SD Card Cart
Replies: 3
Views: 991

Re: Game Raccoon - Open Hardware/Software SD Card Cart

Well, that's exactly what this board is for - helping devs with Sega consoles. I hope it sticks around for a long time. Even those times when I was so burnt out I quit checking other boards, I was always here.
by Chilly Willy
Sun Jul 26, 2020 8:40 am
Forum: Demos
Topic: Game Raccoon - Open Hardware/Software SD Card Cart
Replies: 3
Views: 991

Re: Game Raccoon - Open Hardware/Software SD Card Cart

Very nice! I like that you've been posting all the info about it. It was fun to follow the development. :D
by Chilly Willy
Tue Jul 21, 2020 4:47 pm
Forum: Mega/SegaCD
Topic: mcd-verificator (CD core accuracy tests)
Replies: 24
Views: 5430

Re: mcd-verificator (CD core accuracy tests)

A23-A22/A18-A1 from the Genesis are all connected through to the cart. A21-A19 are fed from the IO chip. When the 32X is disabled, or when it's enabled and the RV bit is set, those lines should be passed through from A21-A19 from the Genesis. When the 32X is enabled and RV=0, A21-A19 come from a com...
by Chilly Willy
Mon Jun 22, 2020 1:06 pm
Forum: Megadrive/Genesis
Topic: Most compatible way to jump to game image on hardware - making my own cart
Replies: 21
Views: 3420

Re: Most compatible way to jump to game image on hardware - making my own cart

Well, at least by having the code written to flash, you don't have the problem of games that write over top of the rom area to crash early versions of rom-backup systems and emulators. I've posted a number of patch files over at Sega-16 that cure the startup problems with a few different games that ...
by Chilly Willy
Sun Jun 07, 2020 12:49 pm
Forum: Sound
Topic: Sega CD Mode 1 support functions for SGDK
Replies: 25
Views: 10987

Re: Sega CD Mode 1 support functions for SGDK

Good to hear. I'll have to remember to make that change in my own stuff. That was a good point - while leaving the CD constantly checking probably doesn't hurt anything, it's better to just shut things down after a while. A menu option in case the user changes their mind later is probably also a goo...
by Chilly Willy
Fri Jun 05, 2020 7:27 pm
Forum: Sound
Topic: Sega CD Mode 1 support functions for SGDK
Replies: 25
Views: 10987

Re: Sega CD Mode 1 support functions for SGDK

EDIT: well, i realize MegaCD led keeps blinking when it is switched on and no cd. It is a bad thing having a MD game with Mode 1 feature, but if you do not put a disc on the CD unit you will have a led blinking for hours... Is there a way to say to the Mega CD to stop detecting CD, or switch off th...
by Chilly Willy
Thu Jun 04, 2020 7:08 pm
Forum: Sound
Topic: Sega CD Mode 1 support functions for SGDK
Replies: 25
Views: 10987

Re: Sega CD Mode 1 support functions for SGDK

Emulators generally don't handle things like Mode 1 since it wasn't used by anything commercial, so it was of no interest to emulator authors. It's like CD32X emulation - not something emulations handle. This is more a real hardware thing.
by Chilly Willy
Sun May 31, 2020 12:16 am
Forum: Sound
Topic: Sega CD Mode 1 support functions for SGDK
Replies: 25
Views: 10987

Re: Sega CD Mode 1 support functions for SGDK

There's a table of vectors in the MD ram for CD related stuff, and you need to alter that if you want to use MD ints AND also keep the CD going. One of the things the CD NEEDS is the level 2 int bumped from the MD side periodically. So in the MD vertical blank, I generate a level 2 int to the CD. Th...
by Chilly Willy
Fri May 29, 2020 12:24 pm
Forum: Sound
Topic: Sega CD Mode 1 support functions for SGDK
Replies: 25
Views: 10987

Re: Sega CD Mode 1 support functions for SGDK

You screwed up some of the conversion into C. Look at the original here write_byte(0xA1200E, 0x00); // clear main comm port write_byte(0xA12002, 0x2A); // write-protect up to 0x05400 write_byte(0xA12001, 0x01); // clear bus request, deassert reset - allow CD Sub-CPU to run and now look at your conve...
by Chilly Willy
Thu May 28, 2020 10:22 pm
Forum: Megadrive/Genesis
Topic: Alternative to Vasm assembler?
Replies: 27
Views: 5724

Re: Alternative to Vasm assembler?

Asmx use @whatever or .whatever for local labels. They're usable until you pass a non-local label. This is pretty standard for many assemblers. So it's like this

Code: Select all

first_label:
    code
    more code
.1
    even more code
.2
    check something
    bmi.b .1
    bne.b .2
    rts

next_label:
by Chilly Willy
Sat May 09, 2020 9:11 pm
Forum: Announcement
Topic: Spritesmind is back
Replies: 6
Views: 4952

Re: Spritesmind is back

Nice to see the site still going strong. A lot of sites have basically given in to the spammers.
by Chilly Willy
Tue May 05, 2020 8:44 pm
Forum: Megadrive/Genesis
Topic: Alternative to Vasm assembler?
Replies: 27
Views: 5724

Re: Alternative to Vasm assembler?

Well, the code is really straightforward, and the bug was pretty easy to spot. Took me maybe two minutes to figure it out. :lol:
by Chilly Willy
Mon May 04, 2020 8:19 pm
Forum: Megadrive/Genesis
Topic: Alternative to Vasm assembler?
Replies: 27
Views: 5724

Re: Alternative to Vasm assembler?

It's a bug in o_Shift in asm68k.c.

Code: Select all

                reg1 = GetReg(data_regs);
                if (reg1 >= 0)
There's no else part that throws an error on the register not being found from the list passed.