For our May 2026 monthly presentation we were given a talk on FPGAs by Zander M1YAP. For those unable to attend the presentation we used Claude AI to make the following notes:
Zander M1YAP recently presented an introduction to Field-Programmable Gate Arrays (FPGAs) and VHDL to our club, demystifying these reconfigurable digital devices with clear explanations and liv demonstrations on a Xilinx Spartan 701 evaluation board.
The presentation began by explaining where FPGAs fit in the landscape of custom logic devices. FPGAs can be reprogrammed on the fly. This makes them ideal for prototyping, education, and applications where flexibility matters more than squeezing every bit of efficiency.
Zander then covered the fundamental building blocks of an FPGA: lookup tables (LUTs) and flip-flops arranged into configurable logic blocks, all connected by a programmable routing fabric. He explained how these simple elements combine to implement any digital circuit. Highlighted dedicated hardware resources like DSP blocks for signal processing and touched on a critical but often overlooked topic: metastability. This phenomenon occurs when a flip-flop samples an input at exactly the wrong moment, and ignoring it can cause unpredictable crashes.
The presentation then introduced VHDL, the hardware description language used to design FPGAs. The key insight is that VHDL describes hardware, not software. All logic runs in parallel, like discrete logic chips on a circuit board, not sequential instructions in a program. Zander presented the basics of the language and the critical distinction between combinatorial logic (outputs depend only on current inputs) and sequential logic (which uses flip-flops to store state).
To bring theory to practice, Zander demonstrated two designs running on the evaluation board. The first showed a simple logic circuit going from VHDL source code through synthesis and programming into the device. The second was more entertaining: a walking LED pattern reminiscent of the scanner light from the Knight Rider television series, showcasing how FPGAs can drive visual displays with precision timing.
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