SpritesMind.Net

I haven't found any sort of timing difference between VRAM activity and whatnot between MD and SMS mode, all the access patterns are identical, video timings identical (AND different from H256 timings). What is different is the FIFO interface being active and no support for updating only the lower h...

LM4880 seems to be adequate. It has better THD and PSRR and looks to be just as easy to use. It should be noted that the output is inverted compared to input (but this has no consequences usually). Only opamps made to drive 75ohms are video stuff but they're usually unsuitable for audio for the most...

All opamps can have the negative power go to GND, and as with all opamps you then have to bias the inputs to somewhere between GND and positive power rail in such case. Now as far as NJM2073 goes, it isn't a regular opamp but a special purpose thing which has internal biasing to reduce external part...

MD biases the signals to its own needed offsets, there's series capacitors on all the signals which are there for that purpose. It is all AC coupled. You cannot do full 5V swing for similar reasons as you get in the cart, the machine still only has 5V power rails. You'll have to experimentally find ...

First of all signal from the DAC etc. is not gonna have a negative components so it is already biased above 0V. You will have to bias it exactly to 2.5V for best dynamic range with most opamps and also bias the opamp to that voltage also. You can use a small linear reg for that or some resistors+cap...

You'll be up for plenty of manual work. I have worked with pulls in past and you absolutely have to verify them all, out of 700 chips, around 100 were dead or damaged (i.e parts of it not programmable etc.). Also pins way not be in the best shape, causing difficulties when soldering. Those stocks ca...

EPROMs have not been produced for years, if you're lucky you can get new-old-stock but you're very likely to get pulls. Your only option is 3.3V parts, having the level shifters and then exclusively using 3.3V parts will cost less than trying to get 5V stuff together. There's far more options and mo...

That EPROM will work but availability might be limited if you intend to make lot of cartridges. They are also likely to be pulls rather than new parts. To save a looooot of time make sure the parts you order are erased before hand. It takes half an hour at least to erase an EPROM. If the MCU has 5V ...

You need full level conversion, resistors aren't going to do anything but current limiting. For single direction stuff you could get away with voltage dividers but signal edges will get poor. For bidirectional signals you'll definitely want actual chips doing the thing. And for power rails you need ...

The video DAC part is figured out pretty much. There's 17 taps on a long resistor structure and each tap is turned on with a control signal to enable certain level on the color channel output. 15 MD mode levels plus two SMS mode exclusive levels.

viewtopic.php?f=22&t=2188

I do stuff like that :

OffsetName EQU 124

MOVE.W OffsetName(A0), D0

EDIT: Exactly what you try to avoid... lol. I don't know of any better solution.

I poll for VBL bit in the VDP in main loop and I also set a flag in the frame interrupt. If main loop sees that the flag is set after all game logic it can assume slowdown has happened and act upon it, when flag isn't set the logic ended before frame did.

I just do 255/34 in my tools and it works for linear and the nonlinear ramp too.

Just for code I have couple old things that can be looked at : My first game on MD, very poor code : http://www.tmeeco.eu/SMD/GBMD11S.RAR Pong game that doesn't use RAM at all : http://www.tmeeco.eu/BitShit/PONG!RAM.ASM And for some less terrible stuff here's a disassembly of the TMSS ROM I made a w...