Search found 116 matches

by themrcul
Wed Sep 14, 2022 12:17 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 70
Views: 130063

Re: Cart Design Questions

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'l...
by themrcul
Wed Aug 24, 2022 2:29 pm
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 70
Views: 130063

Re: Cart Design Questions

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 to...
by themrcul
Sat Jul 30, 2022 9:01 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 70
Views: 130063

Re: Cart Design Questions

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 ~100M...
by themrcul
Tue Jul 26, 2022 7:15 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 70
Views: 130063

Re: Cart Design Questions

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 ca...
by themrcul
Fri Jul 22, 2022 7:11 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 70
Views: 130063

Re: Cart Design Questions

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 an...
by themrcul
Thu Jul 14, 2022 3:38 pm
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 70
Views: 130063

Re: Cart Design Questions

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?
by themrcul
Thu Jul 14, 2022 7:30 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 70
Views: 130063

Re: Cart Design Questions

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 connecto...
by themrcul
Tue Apr 12, 2022 7:04 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 70
Views: 130063

Re: Cart Design Questions

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 mo...
by themrcul
Tue Apr 05, 2022 12:36 pm
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 70
Views: 130063

Re: Cart Design Questions

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 ...
by themrcul
Wed Jan 19, 2022 1:44 pm
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 70
Views: 130063

Re: Cart Design Questions

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 PC...
by themrcul
Sat Jan 15, 2022 3:05 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 70
Views: 130063

Re: Cart Design Questions

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....
by themrcul
Fri Jan 14, 2022 1:34 pm
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 70
Views: 130063

Re: Cart Design Questions

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 parameters...
by themrcul
Fri Dec 31, 2021 4:22 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 70
Views: 130063

Re: Cart Design Questions

Thanks for the suggestions guys. I think it's now a combination of factors or failures. I'm pretty sure there is something wrong with the transport between the CPLD and the Arm, or the parent module which is requesting the data from the SDRAM, not just the SDRAM. Maybe the SDRAM is working fine, and...
by themrcul
Mon Dec 27, 2021 12:20 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 70
Views: 130063

Re: Cart Design Questions

Thank you very much HardwareMan for taking time to help me out. As you can tell I'm very much a newbie with this stuff. Thanks for your tip about bitwise with combinatorial logic - nowhere online in the tutorials I read did it mention that, that is really helpful info. In the meantime I did some mor...
by themrcul
Mon Dec 20, 2021 12:51 pm
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 70
Views: 130063

Re: Cart Design Questions

So it's been a long time. In between my last post I had some issues with my first hardware build, had another son, and have had outside work programming projects that took all my time. I have put off some other things to get some progress done on this project as it was killing me, not being able to ...