A free-running source of 'random' numbers

A linear-feedback shift register driven continuously by a fast CLOCK cycles through its states so quickly relative to human reaction time that whatever value it holds the instant someone presses a button looks effectively unpredictable, even though the whole thing is completely deterministic underneath.

Freezing a value on button press

Feed the LFSR's SHIFT4 outputs into a REG4 (a register that loads on every clock edge) and clock it from the pulse of an edge detector watching a debounced button — so the register captures and holds whatever the LFSR's state happened to be at the exact instant of the press, ignoring the LFSR's continued cycling until the next press.

Mapping 4 bits onto six dice faces

An LFSR's 4 output bits span 0–15, but a die only has six faces. A small comparator-based remap — subtract 6, or 12, whenever the value is 6 or greater, or 12 or greater — folds the range down to 0–5, and adding a fixed 1 turns that into the familiar 1–6. Feed the result into a SEG7 block to display it.

Try it yourself

Build the full chain in the circuit editor — free-running LFSR, debounced button, a register clocked by the edge-detector pulse, range remap, SEG7 display — and press the button repeatedly to confirm the displayed digit changes unpredictably but always lands between 1 and 6.