Assignment to Output

[Seyviour]

Hi!

In autofire, there's a module input paradoxically named out

module Autofire #(
    parameter FREQ = 37_800_000,
    parameter FIRERATE = 10
) (
    input clk,
    input resetn,
    input btn,
    input reg out // <---------
);

Somewhere along the line, out receives an assignment

if (timer == 0) out <= ~out;

Everything works fine regardless, so I'm curious to know what purpose this serves. I'm trying to synthesize nestang with Yosys so this information would be really helpful.

Thanks in advance!!