The Pico PIO has an instruction set and can be programmed.

You write PIO assembly that runs autonomously on a state machine, with explicit timing (e.g., out, in, set, mov, jmp, wait) and cycle‑accurate interfaces. The CPU communicates via small FIFOs, and interrupts are optional; the PIO can be “fire‑and‑forget” for many protocols.

That's cool, I'm not at that level right now, side note I bought an FPGA like 5 years ago and still haven't used it.