[Coco] Educate me about Y-Cables

[Michael Rowen]

It would be useful to have decoding modes for original CoCo 1,2 and one for CoCo3.







RETRO Innovations <go4retro at go4retro.com> wrote:

>I laid out all of the equations in Verilog tonight, and I believe I have 
>replicated the 4 slot MPI functionality with 5 ICs (1 '245, 3 541s, and 
>1 xc9572xl CPLD). A couple thoughts:
>
>  * Found some nice triple output brick-like PSUs, so that does not seem
>    to be a major challenge.  To make for more options, I put a simple
>    2.5mm coax connector on for 5VDC as well and can easily add a
>    Mini-USB for 5VDC power.  I think Mini USB wall warts only do 1Amp,
>    though, so not sure if that would be enough to run 4 carts
>  * I am not convinced more than 4 switched ports are needed, as it
>    seems like 5 ports of an 8 port unit could be "shared", on the last
>    port, assuming the various peripherals will coexist on the bus (I
>    understand the ROMs won't, but an RS232 cart, modem cart, FDC (with
>    ROM), and some other simple cart look to play nice with each other
>    without switching.
>  * That said, I can extend the design to do 8 switched ports (it'll
>    drive the IC count up a bit).
>  * I need to find a cart that has the grounding tabs on it (the Coco I
>    bought only  has a few game carts, which don't have them, so I can't
>    measure.)  Any suggestions?
>  * Looking at the original MPI schematic, it looks like an external
>    peripheral cannot reset the computer, which seems odd, as they would
>    be able to if they were plugged directly into the Coco instead of
>    into the MPI.
>
>Jim
>
>
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