BenchChapter 6: Trees

B37ONE SHOT

The task

V1 drives P0 with a slow square wave. On each rising edge, light the LED on P1 for 30 cycles.

Then put it out and wait for the next rising edge. Every instruction takes one cycle.

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 5 V square at 50 Hz
Resistors: R1 330 Ω
LEDs: D1 yellow
Probes: CH1 and CH2

Key idea

A rising edge is a 1 read after a 0: wait while P0 reads 1, then wait while it reads 0.

Hints

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

Hint 1Show

A countdown loop of SUB 1 and JNZ spends two cycles a pass.

Hint 2Show

MOV A, 14 before the loop gives 28 cycles, and the lines around it make up the rest.

Solution

Reveal the Full SolutionThe complete program for ONE SHOT. 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.

30 cycles of light after each rising edge.

u1SC-2 standard

L: IN P0
JNZ L
H: IN P0
JZ H
MOV A, 1
OUT P1
MOV A, 14
W: SUB 1
JNZ W
OUT P1

CYCLES: 800; at par
ENERGY: 1600; at par
NODES: 1; at par
INSTRUCTIONS: 10; at par