Search found 2377 matches

by TmEE co.(TM)
Fri Apr 19, 2019 8:22 pm
Forum: Video Display Processor
Topic: Help scale and rotation sega genesis
Replies: 33
Views: 5262

Re: Help scale and rotation sega genesis

Even then, a line is still a line regardless of where it is in the frame. There's 262 lines in 60Hz and 313 lines in 50Hz, rest are border, blanking and sync. Lines themselves all consist of border, active part, blanking and sync aswell, and switch can happen in the sync portion. Composition of one ...
by TmEE co.(TM)
Fri Apr 19, 2019 7:45 pm
Forum: Video Display Processor
Topic: Help scale and rotation sega genesis
Replies: 33
Views: 5262

Re: Help scale and rotation sega genesis

Switch must happen not just in horizontal blank, it must be in horizontal sync position of the line. You do your switch at any line you desire during the frame, but the switch itself must happen in sync portion of the line you do it on.
by TmEE co.(TM)
Thu Apr 18, 2019 10:28 am
Forum: Video Display Processor
Topic: Help scale and rotation sega genesis
Replies: 33
Views: 5262

Re: Help scale and rotation sega genesis

Enabling/disabling display isn't gonna do anything with that, video line generation is an autonomous process that runs always and depends on if internal dot clock or EDCLK is used (bit7 or VDP register $07). in H256 (256 pixels + internal dot clock) all pixels are 10 MCLKs long, while in H320 (320 p...
by TmEE co.(TM)
Wed Apr 17, 2019 11:00 pm
Forum: Video Display Processor
Topic: Help scale and rotation sega genesis
Replies: 33
Views: 5262

Re: Help scale and rotation sega genesis

This has been done and it doesn't work really well since the line where the switch happens will have different timings from the rest and that does upset some TVs etc. by making them do weird noises or other oddities. You can reduce the problem by doing the switch during horizontal sync pulse but the...
by TmEE co.(TM)
Sat Apr 13, 2019 9:01 pm
Forum: Video Display Processor
Topic: Is this just shadow effect?
Replies: 1
Views: 718

Re: Is this just shadow effect?

Yes, it is done with Shadow function.
by TmEE co.(TM)
Sat Apr 13, 2019 12:07 am
Forum: Super 32X
Topic: Using 32x as a 3rd plane, possible?
Replies: 28
Views: 5919

Re: Using 32x as a 3rd plane, possible?

Soleil does checkerboard pattern which you could do on the 32X too, but you're not gonna get any real shadow/highlight type stuff without recreating the MD image on 32X side.
by TmEE co.(TM)
Fri Apr 12, 2019 6:54 pm
Forum: Super 32X
Topic: Using 32x as a 3rd plane, possible?
Replies: 28
Views: 5919

Re: Using 32x as a 3rd plane, possible?

32X output can only be above or below MD layer, it cannot do intermediates. Only way you could do some shadowing etc. is to render the output of MD itself on 32X side and apply whatever you want. As far as other stuff goes, no, you cannot really do that. 32X changes the memory map drastically, at be...
by TmEE co.(TM)
Fri Apr 05, 2019 7:28 pm
Forum: Cartridge
Topic: EEPROM mapping for homebrew
Replies: 9
Views: 1489

Re: EEPROM mapping for homebrew

Yeah, that would work better, no bus fights possibility at all ~
by TmEE co.(TM)
Wed Apr 03, 2019 10:14 pm
Forum: Cartridge
Topic: EEPROM mapping for homebrew
Replies: 9
Views: 1489

Re: EEPROM mapping for homebrew

I would use an SPI or µWire EEPROM instead rather than I2C types, they're much easier to talk to (thus less hardware). Here's something I devised a while ago :
Image
by TmEE co.(TM)
Sat Dec 22, 2018 1:00 pm
Forum: SGDK
Topic: VDP_loadTileData CPU vs DMA differences?
Replies: 5
Views: 1607

Re: VDP_loadTileData CPU vs DMA differences?

DMA doesn't cross 128KByte boundaries but wraps around within 128KB block.
by TmEE co.(TM)
Fri Nov 23, 2018 4:06 am
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 378810

Re: New Documentation: An authoritative reference on the YM2612

It is possible to update DAC once every sample if you have cycle synchronity to the YM. I did some tests where YM and Z80 were made to share the clock in MD and I could get unique samples out every 144 cycles. Doing rates between full and half sample rate are very ugly though due to the "resampling"...
by TmEE co.(TM)
Sat Nov 17, 2018 9:59 pm
Forum: Hardware
Topic: Controllers and wrong I/O pin directions
Replies: 9
Views: 2778

Re: Controllers and wrong I/O pin directions

That resistor is the same as 330ohm to ground if it connects to another output, kind of like both outputs driving to a 330ohm load if their states differ (one side high, other low and vice versa). It is a current limit and roughly like lighting up a LED via an IO pin. I'm sure the IO port output dri...
by TmEE co.(TM)
Mon Nov 12, 2018 4:26 pm
Forum: SGDK
Topic: An error check in the 3 line handshake
Replies: 12
Views: 2512

Re: An error check in the 3 line handshake

There are 330ohm series resistors on TH and TL or TR lines which will help in cases using those pins out of the normal way. 330 ohms isn't a huge load to fight.
by TmEE co.(TM)
Mon Nov 12, 2018 3:24 pm
Forum: SGDK
Topic: An error check in the 3 line handshake
Replies: 12
Views: 2512

Re: An error check in the 3 line handshake

Pins on the controller port can be both inputs and outputs and some devices expect the direction to be set different from what a normal controller configuration uses. If two outputs get connected together you will have one or both sides getting damaged sooner or later.
by TmEE co.(TM)
Mon Oct 15, 2018 3:06 pm
Forum: Megadrive/Genesis
Topic: Bus Arbiter and IO Chip Access
Replies: 28
Views: 6201

Re: Bus Arbiter and IO Chip Access

EDCLK generation is made with a little sub board on MD1 VA0 that consists of 3x logic chip. IA14 is probably made by the 00 chip between the RAMs on VA0. Nobody seems to have made a schematic of the board yet though. Full EDCLK pattern is "8aaaaaaa99aaaaaaa8aaaaaaa99aaaaaaa" where each symbol is one...