Search found 244 matches

by mickagame
Tue Feb 16, 2021 11:47 am
Forum: Megadrive/Genesis
Topic: Version Register
Replies: 6
Views: 217

Re: Version Register

Ok thanks for this informations :-)
The value is hardwired inside the chip or come from external (by a jumper for example)?
by mickagame
Mon Feb 15, 2021 7:05 pm
Forum: Megadrive/Genesis
Topic: Version Register
Replies: 6
Views: 217

Version Register

The version register in IO Chip give informations like : Bit(7) : Mode => Pin /LANG from IO Chip (can be set by jumper) Bit(6) : VMode => Pin /PAL from IO Chip (can be set by jumper) Bit(5) : Disk => Pin /DISK from IO Chip Bit(4) : Reserved Bit(3-0) : Version => ??? Is there any signal from IOChip c...
by mickagame
Tue Feb 09, 2021 8:14 pm
Forum: Megadrive/Genesis
Topic: 68K Memory access
Replies: 9
Views: 643

Re: 68K Memory access

When 68K perform long write/read, the 68K in reality do 2 words access.
In what sequence does it?
1) Address + 0
2) Address + 2
Or
1) Address + 2
2) Address + 0

?
by mickagame
Tue Feb 09, 2021 7:41 pm
Forum: Megadrive/Genesis
Topic: Need help to understand sonic rom [Resolved]
Replies: 2
Views: 136

Re: Need help to understand sonic rom [Resolved]

Finally i correct it!
The vdp did not raise cpu v-int for higan core ...
Now sonic is running great with this new core :-)
by mickagame
Tue Feb 09, 2021 7:01 pm
Forum: Megadrive/Genesis
Topic: Need help to understand sonic rom [Resolved]
Replies: 2
Views: 136

Re: Need help to understand sonic rom

After adding log trace the problem seems to be the v-int not catched with higan core : traces with musashi 68k : PC = 0x000018A8 PC = 0x000018AA PC = 0x000018AC V-Int! PC = 0x000018B0 Write Addr : 0x00FFFDF6, data : 0xFFF62A -> 0x0000FF1F PC = 0x000018B4 Write Addr : 0x00FFFDF6, data : 0xFFF62A -> 0...
by mickagame
Mon Feb 08, 2021 8:30 pm
Forum: Megadrive/Genesis
Topic: Need help to understand sonic rom [Resolved]
Replies: 2
Views: 136

Need help to understand sonic rom [Resolved]

I'm actually implementing higan 68k core in my emulator and i would need help in understanding the code of sonic rom. My emulator actually loop at this place : 0029AC TST.b $FFFFF62A.w 0029B0 BNE.b *+$FA => 0029AC With other 68k core (musashi, c68k ...) everything works ok. Edit : if found this in a...
by mickagame
Thu Feb 04, 2021 10:31 am
Forum: Megadrive/Genesis
Topic: VDP Interrupt Processing
Replies: 3
Views: 327

Re: VDP Interrupt Processing

So in my comprehension : - The VDP lower the interrupt line - When receive IACK from cpu the vdp raise interrupt line This is correct? So if VDP lower interrupt line and raise it before the CPU go in interrupt process the interrupt could be ignored (so pending interrupt == interrupt line in low stat...
by mickagame
Wed Feb 03, 2021 8:13 pm
Forum: Megadrive/Genesis
Topic: VDP Interrupt Processing
Replies: 3
Views: 327

VDP Interrupt Processing

I have a question about vdp interrupt processing.
How long the vdp assert interrupt line for Horizontal and Vertical Interrupt?
by mickagame
Wed Jan 27, 2021 12:06 pm
Forum: Megadrive/Genesis
Topic: 68K cycle timing test ROM?
Replies: 11
Views: 6786

Re: 68K cycle timing test ROM?

What could be the reference document in 2021 for 68k timings?
I'l trying to write a 68k core and need a good documentation to implement correct timings.
by mickagame
Wed Jan 27, 2021 6:48 am
Forum: Megadrive/Genesis
Topic: 68K Memory access
Replies: 9
Views: 643

Re: 68K Memory access

The cart can't stop the hardware in the console from responding, so it is generally not proper to respond to a read from an address that the console already does. If you want to be compatible with the Sega CD and 32X, you also need to avoid the address ranges they use. The Teradrive additionally us...
by mickagame
Wed Jan 20, 2021 7:15 pm
Forum: Megadrive/Genesis
Topic: 68K Memory access
Replies: 9
Views: 643

Re: 68K Memory access

thanks for the reply.
So technically the system plugged into the cartridge port could reply to a read/write event adressed to a vdp for example (instead of the vdp himself)?
by mickagame
Tue Jan 19, 2021 8:44 pm
Forum: Megadrive/Genesis
Topic: 68K Memory access
Replies: 9
Views: 643

68K Memory access

I have a question about how the genesis component work.

If i don't a misunderstanding a genesis cardridge has his internal adress decoder.
All 24 pins of the adress bus is connected to a cartridge and the cartridge can be mapped to all 68k Memory Space
=> This is correct?
by mickagame
Mon Nov 30, 2020 7:16 am
Forum: Megadrive/Genesis
Topic: Megadrive ASIA Configuration
Replies: 2
Views: 1425

Re: Megadrive ASIA Configuration

Thanks for reply.
by mickagame
Sun Nov 29, 2020 7:47 am
Forum: Megadrive/Genesis
Topic: Megadrive ASIA Configuration
Replies: 2
Views: 1425

Megadrive ASIA Configuration

Hello, I saw that somes asian megadrive (new) are selled since few years on internet : https://assets.catawiki.nl/assets/2018/9/20/8/8/8/8882c744-bd73-445b-8e20-ac8933d0d5cf.jpg Does someone know how the region jumpers are configured inside (JP1/2/3/4)? PAL ON? NTSC OFF? ENGLISH OFF? JAPAN ON? Some ...
by mickagame
Wed May 13, 2020 5:13 am
Forum: Megadrive/Genesis
Topic: VDP 8x16 Interlace Mode
Replies: 7
Views: 3037

Re: VDP 8x16 Interlace Mode

Thanks for your answers guys. It make sens.