SpritesMind.Net

Thanks guys. Interesting idea to use /CAS2 HardWareMan. The EEPROM I am thinking of using (S29GL032N90TFI040) has a stated total access time of 110ns (this is for random access, not sequential page accesses) - do you think that 110ns is enough time for the EEPROM to be able to get the data if listen...

Ok, so I will need to route the Ready/Busy line from the EEPROM through the CPLD to /DTACK, and tri-state the /DTACK line when in normal operation (ie when the PCB is being used in a Mega Drive) but when the CPLD knows it is being written to via the EEPROM writing device it can switch operation of t...

Thanks very much Chilly. Just so I understand what is going on electrically: The EEPROM will expect the line to drift high with a pull-up resistor. The MD expects the signal to be low to signify "ready". If the line from the EEPROM is hooked up to the MD directly *without* a pull-up resistor to 3.3V...

Hey fellas, I've been progressing with the design, and I've gone back and forward about needing a CPLD or FPGA for the design to work. After a lot of thought and research I have come to the conclusion that everyone else was right from the beginning - I will need a CPLD or FPGA if I am hoping to retr...

Thanks for your continued and great efforts Stef. I'm looking forward to getting my code base up to date with the new version you have released!

You guys are amazing, thanks. How do you know all these things!? Anyway, so if my interface between the MD and the ARM chip is 8bit, I can just hook up the lower 8 data lines, and hook the write high/write low to an AND gate, so that 0V = WRITE, 5V = READ. The ARM chip I am looking at now is the ATS...

Awesome, thanks heaps Mask.
Just to confirm, for 8bit writes, only the first 8 data lines are used, is that correct? Do the upper 8 data lines (D8-D15) go to 0V? Or is their state indeterminate?

Hi everyone, 8 weeks ago my wife and I had our first baby so things have been very busy but I have been planning and thinking about this project lots regardless! I now have a question about the pins on the cart and how write low/high works. It's difficult for me to explain so I'll try to use example...

Awesome, thanks Tiido. I think I'll purchase both and experiment when building the op-amp circuit. Can't wait to get started. Need to design the first PCB that holds most of the components together first though!

Hmmm. It's a shame the NJM2073 looks to be low sound quality.. I have found plenty of linear power regulators which take in up to 6V and spit out both 3.3V and 2.5V - so the mid-point voltage is easily solvable if necessary. In that case, which op-amp would you choose Tiido if you were me? Do you kn...

Thanks Tiido. I have done lots of learning since your last post. I know now that the LM358 for example will only output a puny amount of current, and not enough to surmount 75ohms on a model 1 MD, that is why the output goes through a power buffer circuit that you have designed there. In that case, ...

Thanks so much for that detailed reply Tiido. So, there isn't a problem with sending a 0-5v signal through to cart B1/B3? Isn't the Mega Drive expecting a -1v to +1v signal on those lines? If that's not a problem, that's good news. With the diagrams you kindly posted, how should I go about working o...

Ok, so I just learned that the LM358 op-amp can't create negative voltages from nowhere, so the signal will simply clip when attempting to drive it lower than 0V. Back to the drawing board on that plan at least! The best I can come up with now is some sort of linear regulator to get +1V from the +5V...

Hey fellas, I am gearing up to purchase a few discovery boards for an ARM to test some code with, and hopefully get it playing sound as a first step. What I am wondering is how best to hook the DAC outputs from the ARM chip up to the MD cart side on B1 and B3. From what I have read is the MD expects...

Thanks guys, your help is invaluable. Great news on the Z80 also pulling /TIME low when accessing the /TIME data range. That means that the Z80 can send "play sound" and "play instrument" commands to the ARM chip! I have looked now at using 3.3V flash on the cart pcb extensively. It seems that if th...