Month July 2021

Yellowstone updater screenshot

FPGA In-System Programming: Beginnings

I’ve written several times about Yellowstone’s need for in-system FPGA reprogramming. Once the Yellowstone card is in the user’s hands, the user needs a way to update the FPGA firmware when new versions are released, without requiring a JTAG programmer…

Yellowstone Option Configuration Design

The Yellowstone disk controller’s whole reason for existence is its ability to control any type of Apple II disk drive, but for a few Apple II programs, this universality causes problems. Yellowstone handles standard 5.25 inch drives just fine, but…

current simulation

Transistor Puzzles

I’ve fallen into a deep hole involving current-limiting circuits and current sources, in an attempt to solve a minor problem with the Yellowstone disk controller. In the big scheme of things, this isn’t a very important problem, but it has…

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