There are many well-known fashions among the many 8-bit machines of the Nineteen Eighties, and most readers might rattle them off and not using a thought. They had been merely the celebs amongst a plethora of others, and even for a seasoned follower of the retrocomputing world, there are recent fashions from overseas markets that proceed to shock and delight. [Dave Collins] is treating us to an in-depth take a look at the VTech VZ-200, a funds machine that did notably nicely in Asian markets. On the way in which, we study so much a few very cleverly designed machine.
The meat of the design centres not across the Z80 microprocessor or the 6847 video chip, however the three 74LS chips dealing with each tackle decoding and timing for video RAM entry. That they managed this with solely three gadgets is the exceptionally intelligent half. Whereas there are some compromises just like different minimalist machines in what reminiscence ranges may be addressed, they aren’t enough to derail the expertise.
Maybe probably the most ingenuity is available in utilizing not simply the logic capabilities of the chips, however their timings. The designers of this circuit actually knew the gadgets and used them to their full potential. Right here in 2025, that is one thing novice designers utilizing FPGAs must study; again then, it was realized the arduous means on the breadboard.
All in all, it’s an enchanting learn from a digital logic perspective as a lot as a retrocomputing one. If you need extra, it appears this isn’t the one hacker-friendly VTech machine.
John Dalton, CC BY-SA 3.0.
