BenchChapter 12: Shared buses

B99SIREN

The task

This chip is an SC-4, with registers C and D as well. P1 ticks every 20 cycles.

Two tone siren on P0: add 4 to a phase each tick for 16 ticks, then 8 for 16, and so on.

The phase wraps at 100, and P0 is high while it is 50 or more.

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

Count ticks in C from 0 to 31; C DIV 16 tells the two halves apart.

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

Hint 1Show

The step is 4 plus 4 times C DIV 16.

Hint 2Show

The phase works as in VCO: ADD B, MOD 100, MOV B, A, then DIV 50 for the pin.

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

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

A phase accumulator whose step changes every 16 ticks.

u1SC-4 quad

IN P1
MOV A, C
ADD 1
MOD 32
MOV C, A
DIV 16
MUL 4
ADD 4
ADD B
MOD 100
MOV B, A
DIV 50
OUT P0