The Original Maplin Electronics Board
Back in the day, there was a relatively simple interface board, sold as a kit, by Maplin Electronics in the UK. It used a 6821 PIA to control several I/O ports on a cartridge interface board. I hankered after this board when I was younger, but had this habit of blowing my pocket money on sweets or Panini stickers or something else pointless. So I never got one.
Having developed the SuperSprite FM+ board, and realised just how simple and flexible a CPLD could be, I have for a long time considered developing and releasing a simple electronic developer’s board, which would see a CPLD sitting fully across the address bus, thus allowing the CPLD to decode port addresses, and thus be used in place of the 6821 PIA that was on Maplin’s board. CPLDs can also be used to do a whole lot more than port addressing, and thus the board I plan to develop is limited only by the size of the CPLD and the developer’s imagination.
Getting hold of genuine, reliable CPLDs has been extremely problematic – until I came across a source of some now obsolete PLCC-44 Xilinx XC9536XL and XC9572XL CPLDs. Sadly these are now out of stock at that supplier, but I do have enough to do a run of these boards. The beauty of the PLCC-44 chip is that you can start with the 9536, and if you run out of space in your Verilog/VHDL code, you can swap it for a 9572.
I asked users on the Coco and Dragon Facebook groups for suggestions of names for this board, with the constraint that I wanted any name to be prefixed with ‘Super’, continuing the naming theme of the SuperSprite FM+. Lots of people responded with some great names, but ultimately it was the cumulative suggestions of Rebecca Bryan and Brian Blake that won.
Rebecca suggested SuperBreakout – I really liked that, but it was still trademarked in the area of computing. Brian then went one step further with the suggestion of SuperBob – the Super Breakout Board. I really liked that name. Not only was it a fun acronym, but it also gave connotations of Bob the Builder – and after all, this will be a builder’s board.
I currently have the prototype boards on my desk. These are waiting to be soldered up, and for some CPLD code and a sample electronic circuit – to be put together. It will likely be something audio related – maybe a simplified version of the audio parts of the SuperSprite FM+ board – which could play the YM2149/YM2413 music demoed for the larger board. As soon as I’d created that board though, it became apparent I’d included a massive constraint on the CPLD, by tying the ‘global’ pins to the address bus. So I almost immediately re-worked the tracery around the CPLD, and further improved the board. You can see the prototype and next version below.