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  1. 24 x 21 bits is 3 bytes x 21 = 63 bytes. 24 x 24 would be 3 x 24 = 72 The first fits nicely into memory along binary boundaries (2,4,8,16,32,64). The second, not so much. Thus, the first allows the VIC-II to make a rule: sprite data must be aligned on a 64 byte boundary Then, the pointer for the sprite data doesn't need to store the lower 6 bits of the address, since it will always be 0.
  2. Anytime you can meet fellow enthusiasts face to face is a fun time! Jim
  3. I can't say for sure, but I think TI notated things that way on the 99/4a. FOr instance, the addresses are A0-A15, where A15 is the LSB. I'd expect the data lines to be the same
  4. This is a classic "crystal into oscillator" circuit. I could explain it, but others do much better than I https://learnabout-electronics.org/Digital/dig51.php https://electronics.stackexchange.com/questions/489785/2-pin-crystal-oscillator-crystal-oscillator-circuit-explanations You can use the same circuit for any device that needs a "clock" input, not a crystal input (BTW, ICs that use a crystal input just put the left hand circuit on the IC itself. The 2 inverters on the right "boost" the signal from the generator, which can't take a lot of load itself. ONly 1 is needed, in my opinion, becausing inverting the clock won't change anything, so turning it right side up is unneeded, but maybe they had an extra gate and it was easiest to just put it in play.
  5. brain

    RDY pin on 6502

    You can't stop the clock on most 6502s, as they CPU is not a static design (it will lose state if not clocked often enough). Thus, RDY exists. Jim
  6. It looks there is enough data there to recreate the mod, but I agree that the lack of attention suggests some issues. I'm working on a 4MHz design, but not using this idea. Not sure if it'll pan out though. Jim
  7. Hmm, flow control. OK. Well, good that it works for you. Jim
  8. Try leaving off the &C0 and seeing if that helps. Also, if you have a Serial line tester, those are always good to see the difference in signals from the two setups. Jim
  9. Discord is pretty active for CoCo: And the mailing list has been active at times. Jim
  10. Hmmm, there's not a lot of information here, but I can assure you TCPSER works with PETs. 🙂 If the terminal program on the PC works, then at most it's a configuration issue. Try providing the command line you're using here, and turn on debugging and tracing : -l7 -tsSiI and post some of the output here. TCPSER has to play with the RS232 lines to create a DCD line for the PET, and thus you might need a modified null modem cable (as noted in the github repo README), or you might need to tie DCD high all the time... Jim
  11. It might be because the game requires the VIAs to be in the reset state and unconfigured, probably taking shortcuts since it's safe to assume registers are at reset states. And yes, a hard reset would wipe RAM. You might be able to accomplish what you want, though, by using a RAM expansion cart like UltiMEM (caveat, I sell that unit) which has ram that you can writeprotect.
  12. Does it have to be ColecoVision specific? I know some other platforms desperately looking for 76489-based content. Jim
  13. Short answer is absolutely YES. Memory and BASIC have lots of links, so do a google search for those (there were lots of board revs, so it's tough to give general instructions here. Composite is possible as well. Ed Snider offers that kit (https://thezippsterzone.com/). It does require ditching the RF box.
  14. Hm, that is odd, as that's an error from programming, not compilation (I did, though, find a way to fix those two warnings in the latest HEAD revision). Does it have the same issue on any other Arduino boards you might hying around? I'll check a few here. Jim
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