Not long ago, I picked up an old point-of-sale terminal at an electronics surplus store. After discovering a cool little Z-80 based computer inside, and reverse-engineering the hardware, I decided to reprogram it to unlock the music hidden inside magnetic…
I’ve finally made some visible progress in turning this Tranz 330 point-of-sale terminal into a general purpose Z-80 computer. It prints my name on the display! I may faint from the excitement. OK, it’s not much to look at yet,…
I found an old credit card terminal at an electronics surplus store recently, and bought it to tinker with. $5 at Weird Stuff in Sunnyvale! This Verifone Tranz 330 was used to process credit card transactions in the 80’s and 90’s,…
After four months of inactivity, here’s some documentation for the Tiny CPU instruction set. opcode x0 x1 x2 x3 x4 x5 x6 x7 x8 x9 xA xB xC xD xE xF 0x SUB abs SUB imm SUB abs,X ADD…
I think I’ve found answers for all the big questions about Tiny CPU’s design, and I’m ready to start creating the final schematic and board layout, save for one issue: pin constraints. I need to constrain which signals are assigned…
Tiny CPU just barely squeezes into a 128-macrocell CPLD, and so I’ve designed a companion chip called Tiny Device to handle other interface functions. It utilizes a second CPLD, and was originally envisioned as a simple address decoder, but its…
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