Re: Maplin Z80 CPU card
If the 3D printed case is still on the drawing board may I suggest either an open slot or a knock-out panel where the edge connector is so that Sinclair Spectrum peripherals like the Currah Microspeech, etc, can be plugged in (The layout of the double sided edge connector on the Maplin Z80 CPU is almost the same as that of the Sinclair Spectrum, presumably intentionally so).
Unfortunately no matter how you design it, it is unlikely that my Maplin Z80 CPU system, in its current form, will fit inside it. For well over half of its life now it has been attached to an MPF-IO PCB originally intended as an add-on for the 'Microprofessor' system - I bought this when Greenweld had some for sale many years ago. The address decoding on the MFP-IO board is such that none of the memory or I/O addresses on it clash with those on the Maplin system, so it was just a simple matter of wiring all the buses together.
The 8251 UART and Z80-CTC (as baud rate generator) are used in conjuction with additional code in the M12 EPROM to provide serial download of Intel Hex code through the RS232 connection at lower left on the MFP-IO PCB.
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