![]() Selection made…īuffers would remain the same as the mini-MPI, 74ABT16245’s, perfect for this application. Two of these would offer a decent serial expansion without getting crazy on cost or board space. Price and performance pointed me straight at the NXP SC16C550B, a capable current incarnation of the 16550 rated for higher speeds and with 16-byte FIFO buffers. Researching this, it became apparent pretty quickly that of the original UART lines that existed in the past had pretty well died out except for the 16550, several examples of which are in current production in SMT quad flat packs. I had a few criteria here it needed to be an actual serial UART, it needed to be current production, and it needed to be SMT. Next, selection of the serial interface components… I was sold on the YMF-262, or at least on trying it. Especially once I discovered the required chips were available, and in fact, relatively cheap. Listening to the quality of sound that can be reproduced using this chip on YouTube videos and the like was enough for me. The ‘262 seemed a good fit for the project, and offered a lot of capability for our 8-bit CPUs to work with. The MPI portion of the design was straightforward enough, given my previous experience on the mini-MPI, which left selection of components for the extended features.Įarlier Facebook group discussions on sound chips had steered me to the Yamaha YMF-262M (OP元) as a possibility. This fit in nicely with the project I was beginning, and if that’s what the group wanted, then I’d try to do just that. It would be a multi-slot MPI with a sound chip and serial ports. About the time I was starting the design, I happened to catch an episode of CoCo Talk, where sound chips and other expansions were being discussed.ĭuring the discussion, the idea of the ultimate CoCo expansion started to take some shape. ![]() The point is, the community needs more MPI options… I felt the time was right to produce another design to offer alongside the mini. As of this writing they go for $150-$200 each, when they are available, which certainly isn’t all the time. I had been thinking for a while about doing something with more slots as well, because there just aren’t enough original 4-slot MPIs out there. ![]() The mini-MPI that I designed earlier has been available for a while now, and finding a place with quite a few Color Computer enthusiasts out there.
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