Search found 95 matches

by Gigasoft
Thu Feb 25, 2021 12:34 am
Forum: Megadrive/Genesis
Topic: Problem Expanding Super Monaco GP
Replies: 8
Views: 165

Re: Problem Expanding Super Monaco GP

The register dumps are taken at different times and are therefore barely useful. Looks like it crashes somewhere around ED1Eh. You need to inspect the stack to find the exact location where it crashed.
by Gigasoft
Wed Feb 24, 2021 1:51 am
Forum: Megadrive/Genesis
Topic: Problem Expanding Super Monaco GP
Replies: 8
Views: 165

Re: Problem Expanding Super Monaco GP

Did you also update the ROM size field in the ROM header at offset 1a4h?
by Gigasoft
Tue Feb 16, 2021 3:42 am
Forum: Megadrive/Genesis
Topic: 68K inner workings
Replies: 6
Views: 5363

Re: 68K inner workings

Some reconstructed missing instructions, whose microcode addresses do not follow from the schematic. There are, however, columns that look like a possible result from an error in vectorization involving the decoder lines for these instructions. I126a. 0100111001110101 (rts) (1) C<=D D<=[DATA:Am].B A...
by Gigasoft
Mon Feb 15, 2021 6:29 pm
Forum: Megadrive/Genesis
Topic: 68K Memory access
Replies: 9
Views: 664

Re: 68K Memory access

Instructions that perform accesses in reverse order are: - movem.l to -(Am) - move.l to -(Am) - eori.l, ori.l, andi.l, subi.l, addi.l, subq.l and addq.l to memory - negx.l, clr.l, neg.l, not.l on memory - subx.l and addx.l -(An), -(Am), both reading and writing All other accesses happen in forward o...
by Gigasoft
Sun Feb 14, 2021 2:59 am
Forum: Megadrive/Genesis
Topic: 68K inner workings
Replies: 6
Views: 5363

Re: 68K inner workings

Part 2: B96. 0000XXX100XXXXXX (btst dynamic memory) B97. 0000100000XXXXXX (btst static memory) (1) PC<=A C<=BIT&D CCR<=Flags.L A<=A+2 CHECK [PROGRAM:A] (2) D<=[LAST] PREFETCH[LAST] FETCH F<=IMM End B98. 00001000X1XXXXXX (bchg, bset static memory) B99. 0000XXX1X1XXXXXX (bchg, bset dynamic memory) (1)...
by Gigasoft
Sun Feb 14, 2021 2:59 am
Forum: Megadrive/Genesis
Topic: 68K inner workings
Replies: 6
Views: 5363

Re: 68K inner workings

Here are the rest of the instructions. Note: A.Count refers to bits 0-5 of the A register. Instruction patterns without microcode: #0. XXXXXXXXXX1111X1 except #2, #3 illegal #1. XXXXXXXXXX11111X except #2, #3 illegal #2. 1110XXXXXXXXXXXX #3. 011XXXXXXXXXXXXX #4. 0000XXX011XXXXXX except #5 illegal #5...
by Gigasoft
Fri Jan 04, 2019 8:46 pm
Forum: Megadrive/Genesis
Topic: 68K inner workings
Replies: 6
Views: 5363

68K inner workings

Hi, I just wanted to share some of my notes I made a while back. This is based on Galibert's schematic, so in these notes the chip is assumed to be oriented such that the A13 pin is on the upper left. A lot of this is probably well known already, but I thought it'd be nice to have it all in one plac...
by Gigasoft
Mon Oct 27, 2014 10:00 pm
Forum: Sound
Topic: SMPS status ?
Replies: 11
Views: 8630

Really? Same? In sonicretro there are three different tables for three different SMPS versions for coordination flags. What I mean is that within any one of these versions, the format for music and sound effects is the same (except for the extra byte in the track header for which channel to use). W...
by Gigasoft
Fri Oct 24, 2014 11:45 pm
Forum: Megadrive/Genesis
Topic: Interruption mask
Replies: 2
Views: 1998

IRQ6: vblank
IRQ4: hblank
IRQ2: controller port TH pin
by Gigasoft
Fri Oct 24, 2014 10:56 pm
Forum: Sound
Topic: SMPS status ?
Replies: 11
Views: 8630

Strange, no info about ASDR here. I see that there is coordination flag for changing volume of PSG channel, but it's not ASDR support. May be it's another custom modification of SMPS? Well, not exactly ADSR, but there's something they call the "flutter table" which is just an arbitrary curve. And, ...
by Gigasoft
Fri Oct 24, 2014 6:28 pm
Forum: Sound
Topic: SMPS status ?
Replies: 11
Views: 8630

All playing music keeped in Z80 memory, so you have restriction on size of sequence. No, most games that use SMPS keep the music in ROM. The only game that I know of that loads it into Z80 RAM is Sonic 2. 6) PSG ASDR emulation. (correct me, if it's implemented in SMPS) Yeah, SMPS supports volume en...
by Gigasoft
Wed Oct 22, 2014 8:38 pm
Forum: Sound
Topic: General guidelines on working with PSG/YM2612 natively
Replies: 49
Views: 25525

Sonic 1 uses the Z80 exclusively for playing DAC samples, as does Phantasy Star 4. You also don't need to be reading things from ROM. The 68000 could write data into Z80 RAM as needed. For example, Sonic 2 has all its music in compressed form, and decompresses each tune into Z80 RAM before playing i...
by Gigasoft
Sat Aug 16, 2014 8:23 am
Forum: Megadrive/Genesis
Topic: Sonic speed ?
Replies: 7
Views: 3581

And why would it be laid out like that? Usually your levels are made out of larger tiles, and you only generate rows and columns of VRAM tiles when needed. Otherwise you run out of space fast. In the rare event that you do have a tilemap in ROM or RAM, it's probably still better to get the column da...
by Gigasoft
Wed Aug 06, 2014 5:41 pm
Forum: Megadrive/Genesis
Topic: Emulator-dependant bug
Replies: 7
Views: 3111

Looks like you are failing to synchronize accesses to the VDP. Make sure that you don't get interrupted in the middle of accessing the VDP by code that also accesses the VDP. Data uploads should preferably happen during blanking.
by Gigasoft
Tue Jul 15, 2014 12:14 pm
Forum: Sound
Topic: Need help w/YM2413
Replies: 4
Views: 5562

I can't see any problem with the calculation. Could you be reading the VGM file wrong?