BenchChapter 5: Half duplex

B33BEACON

The task

A beacon flashes twice, then rests. P1 ticks every 10 cycles and P0 drives the lamp.

Light it on the first and third tick of every twelve, and keep it dark on the other ten.

The chip's ports, each with its kind and the parts its signal reaches. Cyan reads, lemon writes.

IN P1 counts the ticks. MOD 12 gives the place in the pattern, 0 to 11.

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

Hint 1Show

Places 1 and 3 light the lamp. They are the odd places below 5.

Hint 2Show

Rule out the places from 5 up first, then MOD 2 picks the odd ones.

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

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

Two flashes, then a long rest.

u1SC-2 standard

L: IN P1
MOD 12
SUB 4
JG OFF
ADD 4
MOD 2
OUT P0
JMP L
OFF: MOV A, 0
OUT P0