SpritesMind.Net

Thank you very much for the confirmation TmEE, that means a lot.
I'm almost ready to get the 3rd revision of my cart fabricated by JLCPCB after a long hiatus on this project.
Hopefully my fixes will mean it works this time!

Ok so I did some experimenting with a MOFSET, specifically an N-type enhancement mode MOFSET, the 2N7002.
I have done some researching about how MOFSETs work, but this is the first time I am attempting to implement one, so I am just checking here to see if I am doing something wrong!

I connected ...

Hi everyone,
After a long hiatus, I am gearing up to make my third version of the PCB, hopefully this one will work correctly.

I have one question before I commit to getting it fabricated that I wanted to ask, and that is about inducing a soft reset from my cart.

I know that the Mega Drive exposes ...

Hey fellas,
Just letting y'all know I've trimmed up some bits and pieces of the PCB and made an order for it, along with a 16bit logic analyzer from Aliexpress.
I hope this combination will help me track down what is going wrong with my original design. It will be a few weeks before delivery and I ...

Hi guys,
I've knocked up a test PCB to sit between a Mega Drive and any cartridge that I plug in.

Life is busy (as I assume it is for everyone here!), and I've done it in a way that orders the address and data lines in a easy way for me to plug a logic analyzer into.

But before I do the finishing ...

Ok thanks Mask,
I see with a quick Google that the DMA controller runs at ~13MHz - so I will need ~30MHz to get a reading of what is going on there.
That means if I'm debugging DMA I'll only be able to do a max of 9 channels to ensure I'm running at 32MHz.

Other Logic Analyzers with guaranteed ...

Thanks guys,
I just missed out on an Amazon sale for a 32 channel LA, but have found a 16 channel one that looks ok.
Without the sale the 32 channel one is just too expensive, at ~$400AUD.

But before I hit the buy it now button on the 16 channel one, I just wanted to check, if this logic analyser ...

Hi Charles and cero,
Thanks to you both for your posts. Sorry for the length of my reply but I want to get everything down in case that helps me get to a solution!

About the TMSS, I'm not even getting that far. When I load the Sonic the Hedgehog ROM onto my SDRAM cart plugged into my Mega Drive 2 ...

Hi cero, thanks for your reply.
But wouldn't I need more than 16 lines? I'd need 5x control lines, 22 address and 16 data lines alone to see accurately what's going on.
Or am I missing something?

Hi everyone,
So I've been going back and forward with this thing, and while I have made some baby steps to make it reliable this time (at least within it's own world), I simply can't get it to work on the real Mega Drive.

As I wrote above, I made a test PCB to send commands through the edge ...

Thanks again Charles,
Your posts inspired me to get my test pcb working.

I programmed the code for the SAM3U microcontroller to receive commands from the computer via USB to set address, control and data lines manually, along with a dummy "read from cart" command sequence. I'll be able to give it ...

Thanks very much Charles for taking the time to reply to me.

I'm afraid I don't have a logic analyzer. I was hoping to get by without one, but it may be the case that I need to bite the bullet and purchase one. That being said, I don't know how I would use one to monitor the 68K bus - I'm very much ...

Hi guys,
So I have gone ahead and tested each address line on the cart PCB using Intel's Debug Probes feature of Quartus, along with the data lines in both directions with a multimeter and all the lines are on the correct pins and working.

But I still can't get the Mega Drive to boot. I start the ...

Ok so I repaired VA7. It took me to the limits of my soldering ability to do so. It turns out there was a solder bridge formed behind the VA7 pin and an adjacent pin on the level shifter as well. I had to bend the pins on the level shifter to fix it among other things and thankfully nothing snapped ...

Hi guys, so I have gotten SDRAM reading and writing reliably now.
My own attempt to write a controller for it failed - it just didn't work, even though it seemed like it should when I compared the simulator to the datasheet.

Regardless I got the previous controller working by changing the ...