BenchChapter 9: Special nodes

B68TRACKER

The task

P0 reads a target on CH1. P1 charges C1 through R1, and P2 reads C1 back.

On each tick of P3, raise P1 while C1 is below the target and lower it otherwise.

CH2 follows CH1.

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 1.2 V triangle at 10 Hz and V2 2.5 V
Resistors: R1 22 kΩ
Capacitors: C1 1 µF
Probes: CH1 and CH2

Key idea

Subtract C1's reading from the target: a positive result means C1 needs more charge.

Hints

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

Hint 1Show

Any nonzero value drives a digital pin high, so a positive difference can go straight out.

Hint 2Show

IN P3, IN P2, MOV B, A, IN P0, SUB B, then JG past a MOV A, 0 to OUT P1.

Solution

Reveal the Full SolutionThe complete program for TRACKER. 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.

Charge while C1 is below the target.

u1SC-2 standard

IN P3
IN P2
MOV B, A
IN P0
SUB B
JG H
MOV A, 0
H: OUT P1

CYCLES: 618; at par
ENERGY: 1236; at par
NODES: 1; at par
INSTRUCTIONS: 8; at par