Search found 95 matches
- Thu Feb 25, 2021 12:34 am
- Forum: Megadrive/Genesis
- Topic: Problem Expanding Super Monaco GP
- Replies: 9
- Views: 14254
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.
- Wed Feb 24, 2021 1:51 am
- Forum: Megadrive/Genesis
- Topic: Problem Expanding Super Monaco GP
- Replies: 9
- Views: 14254
Re: Problem Expanding Super Monaco GP
Did you also update the ROM size field in the ROM header at offset 1a4h?
- Tue Feb 16, 2021 3:42 am
- Forum: Megadrive/Genesis
- Topic: 68K inner workings
- Replies: 6
- Views: 13875
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...
- Mon Feb 15, 2021 6:29 pm
- Forum: Megadrive/Genesis
- Topic: 68K Memory access
- Replies: 9
- Views: 12424
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...
- Sun Feb 14, 2021 2:59 am
- Forum: Megadrive/Genesis
- Topic: 68K inner workings
- Replies: 6
- Views: 13875
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)...
- Sun Feb 14, 2021 2:59 am
- Forum: Megadrive/Genesis
- Topic: 68K inner workings
- Replies: 6
- Views: 13875
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...
- Fri Jan 04, 2019 8:46 pm
- Forum: Megadrive/Genesis
- Topic: 68K inner workings
- Replies: 6
- Views: 13875
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...
- Mon Oct 27, 2014 10:00 pm
- Forum: Sound
- Topic: SMPS status ?
- Replies: 11
- Views: 17346
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...
- Fri Oct 24, 2014 11:45 pm
- Forum: Megadrive/Genesis
- Topic: Interruption mask
- Replies: 2
- Views: 3502
- Fri Oct 24, 2014 10:56 pm
- Forum: Sound
- Topic: SMPS status ?
- Replies: 11
- Views: 17346
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, ...
- Fri Oct 24, 2014 6:28 pm
- Forum: Sound
- Topic: SMPS status ?
- Replies: 11
- Views: 17346
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...
- Wed Oct 22, 2014 8:38 pm
- Forum: Sound
- Topic: General guidelines on working with PSG/YM2612 natively
- Replies: 49
- Views: 54035
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...
- Sat Aug 16, 2014 8:23 am
- Forum: Megadrive/Genesis
- Topic: Sonic speed ?
- Replies: 7
- Views: 6231
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...
- Wed Aug 06, 2014 5:41 pm
- Forum: Megadrive/Genesis
- Topic: Emulator-dependant bug
- Replies: 7
- Views: 5667
- Tue Jul 15, 2014 12:14 pm
- Forum: Sound
- Topic: Need help w/YM2413
- Replies: 4
- Views: 10480