After working extensively on the ZXIO Blog series, I aimed to create a memory-mapped I/O board ideal for experimenting with ZX BASIC, as the ZX81 lacks the ability to use IRQ-mapped devices without resorting to machine code routines. The end result is the ZXIO V2, which is based on the use of an 8255A Programmable Peripheral Interface IC. Apparently, I wasn't the only one wishing for such a device. The blog series was extremely...
