BenchChapter 5: Half duplex

B24COINCIDENCE

The task

V1 and V2 send square waves to P0 and P1 at different rates.

Light the LED on P2 only while both inputs are high.

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 250 Hz and V2 5 V square at 100 Hz
Resistors: R1 330 Ω
LEDs: D1 green
Probes: CH1, CH2, and CH3

Key idea

When P0 reads 0 the answer is 0, whatever P1 says.

Hints

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

Hint 1Show

JZ jumps when A is 0, so it can skip reading P1.

Hint 2Show

Read P0. If it is 0, write that 0. If not, read P1 and write what it says.

Solution

Reveal the Full SolutionThe complete program for COINCIDENCE. 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.

The LED lights only while both inputs are high.

u1SC-2 standard

IN P0
JZ W
IN P1
W: OUT P2

CYCLES: 400; at par
ENERGY: 800; at par
NODES: 1; at par
INSTRUCTIONS: 4; at par

Another way: Mul

A second program that also passes, by a different road, at a cost on INSTRUCTIONS.

The product of the two readings is 1 only when both are 1.

u1SC-2 standard

IN P0
MOV B, A
IN P1
MUL B
OUT P2

CYCLES: 400; at par
ENERGY: 800; at par
NODES: 1; at par
INSTRUCTIONS: 5; over par