BenchChapter 12: Shared buses

B97FUSE

The task

P0 reads the load current on CH1. P1 switches the lamp through Q1; CH2 is its drain.

Turn the lamp on. Each tick of P2, add (current minus 40) DIV 4 to a heat count, never below 0.

When the heat passes 100, turn the lamp off for good.

The board

The chip's ports, each with its kind and the parts its signal reaches. Cyan reads, lemon writes. On a narrow screen, scroll the board sideways to see all of it.

Sources: V1 3.5 V, V2 2 V square at 12.5 Hz, V3 1 V square at 6.25 Hz, and V4 5 V
Resistors: R1 100 Ω and R2 330 Ω
LEDs: D1 yellow
Transistors: Q1, an N channel MOSFET
Probes: CH1 and CH2

Key idea

Keep the heat in B. A sum that is not positive becomes 0.

Hints

Each hint goes a step further than the one before. Open them one at a time.

Hint 1Show

Without the floor at 0, the heat sinks past minus 128 and wraps to a large number.

Hint 2Show

Once tripped, the program must stay put: a loop that jumps to itself does.

Solution

Reveal the Full SolutionThe complete program for FUSE. Open it only when you want the answer.

The reference program

The game's own solution. It passes every test and scores exactly par on every benchmark.

A thermal model with a floor at 0 and a latched trip.

u1SC-2 standard

MOV A, 1
OUT P1
L: IN P2
IN P0
SUB 40
DIV 4
ADD B
JG K
MOV A, 0
K: MOV B, A
SUB 100
JL L
MOV A, 0
OUT P1
S: JMP S

CYCLES: 800; at par
ENERGY: 1600; at par
NODES: 1; at par
INSTRUCTIONS: 15; at par