Bah Humbug


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Ace

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A few months ago I found I had enough time on my hands to get on with something I 've been planning for 20+ years and that was to create a new Jupiter Ace. At one point I'd started porting the ROM to the Raspberry PI bits of it even run, but the problem was that the PI is quite a closed system finding out the details of the CPU and Graphics system is difficult and hidden behind a veil of secrecy and IP. The system I wanted to create would be simple and easy to understand at all levels. The first step was to find some schematics in a system I could get for free. Bodo Wenzel had done some nice ones here but in OrCAD which costs money. He did, however, provide images of the work so off I set with the free version of Eagle CAD. I downloaded the PDFs to get a good look. I translated the above eventually to Which is available in KiCad format here . Then built a cut down version to show the diagrams were correct. All the routing is done by FreeRouting because I'...
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Interrupted

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It has been a while. Full-time paid employment means I have enough cash to finish this but limits the time I can spend finishing it. The current state of play it that I have added some SMDs to get in some practice with those. One of the SMDs is a frequency multiplier so that with the original crystal to drive the video I can vary the CPU speed from the 3.278MHz of the original ACE up to 19.668MHz and perhaps beyond. I've also made some modifications to make the KIO optional and enable full ACE compatibility. The KIOs are very difficult to get hold of and with Z84C15 and Z182 available these seem like the best CPU to be going forward. The fastest CPU I have is 20MHz and while I had to up the speed of the RAM, everything else seem happy on the CPU side. The Video was less happy, but I am not 100% convinced that was a speed problem. The multiplier I'm using on this board is a Renesas 512MLF , which is pin compatible with the On Semiconductor NB3N502DR2G , though the multiplicat...
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CPLDs & Xilinx

One of the problems with GALs is the development tools which are way out of date. Though preparing the files by hand doesn't seem to be too difficult. The other problem is the relatively small number of pins. The next step up is  Complex Programmable Logic Devices ; CPLDs come in a far larger variety and there or some development kits available for the older legacy designs.    Some of Microchips' offerings, such as the ATF1504AS, can be programmed using WinCUPL like GALS. They also offer a full system such as ATF15XX-DK3-U that can be bought from the likes of Mouser at reasonable prices, though it is quite a high value for reasonable. Lattice & Intel also do similar things.   Having done a bit of research and found that Xilinx has released their old Integrated Synthesis Environment; ISE system, which does schematic capture. I decided to check out that route. Schematic capture is not used that much, but, I find it very useful when translating the logic designed i...
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