On 09/08/2013 09:12 AM, HÁRSFALVI Levente wrote: > > (Personally, I find this little device a pretty brilliant one, > with/despite its simplicity, especially whenever I make an attempt to > build some of its functionality from TTLs ;-). Probably not much more > complicated in itself than a usual TTL bidirectional bus driver, yet > very efficient to use in practice. The only thing I'm missing is a reset > input (which probably wouldn't fit the DIP20 package)). Same here. Whenever I try to think of a replacement using only TTLs, it becomes a surprisingly complicated circuit if I want to emulate all funktionality from the datasheet. If you only want to replace the 6529 used for the keyboard in the 264 series, you _might_ be able to get away with a 374 (pinout adjusted). Luckily, the 6529 does seem to be pretty stable, so far I didn't have a broken one. > BTW, speaking of the keyboard scan schema of the early "TED" series, > IMHO it's interesting that both the Sinclair ZX80 and ZX81, and AFAIR > even the Spectrum did make it into production with this "address lines > directly used in the keyboard scan process" method |-) . Yes, but they used the address lines in the ZX, not, as in the early 264 models, the data lines. This way the row scanned was determined by the address you used to poll the single ULA register of the spectrum. Not a bad idea, but it meant that you had the keyboard matrix hooked up to the address lines. I doubt you would be able to pass FCC certification nowadays with a design like this. >> and if so, what are the implications of using a >> standard Atari/C64 joystick, and adapter?? > > IMHO not many, other than TED sensitivity (TED broken input latch > phenomenon, not really investigated yet) and active electronics in > joysticks not really working, if there are some. You should be able to make a joystick with a working auto-fire circuit that works on a 264 computer since the joystick port also supplies a real GND. But it would mean some extra electronics inside the joystick. So far I have never broken a TED keyboard port, but then, I never plug or unplug anything with the system running. Gerrit Message was sent through the cbm-hackers mailing listReceived on 2013-09-08 08:01:00
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