[Coco] Educate me about Y-Cables

[RETRO Innovations]

On 2/20/2015 8:09 PM, Zippster wrote:
> I guess I was really thinking something very simple mainly so I could use 1 additional
> slot.  Like an SDC along with a real floppy, or sound cart, or RS-232, etc.
>
> I think someone else is working on a new MPI (Retro Innovations?) so I didn’t really
> want to get into that at the moment.  Buffering and some DC power from a wall-wart is easy
> enough though.  I'll see what I can come up with.
Well, don't quit on my account.  But, slow though I may be, here is what 
I have done:

  * I made an order for some 40 pin .100" edge connectors
  * Ordered a batch of xc9572xl CPLDs, which I can program
  * Started working on the design, which is mainly in the CPLD. The CPLD
    will hold the IO register and handle the logic on the MPI in the
    PAL, the LS374, LS367, LS139, LS368, LS74, LS30, and LS153
      o buffer all the same lines as the original MPI, but I am planning
        to use 74abt541s instead of 74ls367s for the address lines and
        such, but using a 245 for the data lines, as before.
      o put the following Coco lines into the cpld (32 lines)
          + 8 data lines
          + 16 address lines
          + CTS
          + SCS
          + Q
          + E
          + SLENB
          + CART
          + RESET
          + R/W
      o and from the cart slots (12)
          + 4 cart lines
          + 4 SCS lines
          + 4 CTS lines
      o and to/from switches and LEDS (6)
          + 2 lines for initial slot selection
          + 4 lines for LEDs
      o That uses 50 of 52 lines on the CPLD (VQ64 footprint), and I
        think I am still missing a few signals I need.  I can forego the
        upper 8 address lines (like the real MPI), but would prefer not to.
  * Bought a small ATTINY AVR to do the switch to 2 slot select line
    conversion, though might do something else.

I have an EAGLE footprint for the edge connector and the female version, 
but am always interested if there is one that includes the grounding 
fingers.

Since I am planning to be at CocoFEST, I am trying to get this done in 
time to bring.

JIm