NesLinearCounter

Struct

Source: AudioTypes.h

Description

NES APU linear counter state for the TRIANGLE channel.

The linear counter is a quarter-frame clocked 7-bit countdown shared with the TRIANGLE channel. A write to $4008 sets the reload value (lower 7 bits) and the reload flag. On the next quarter-clock:

• if reloadFlag is set, the counter is loaded from reloadValue;
• else if the counter is > 0, it is decremented;
• if the shared control flag (i.e. NesLengthCounter::halt) is clear, the reload flag is also cleared.

The shared halt flag is read through the lengthCounter pointer, which is bound in AudioChannel::reset(). This avoids duplicating the flag and keeps $4008's control bit and $400B's halt bit behaviour in lockstep with the canonical NES semantics.

When the linear counter is enabled (linearEnabled == true) and the counter is 0, the TRIANGLE sequencer is gated per-sample (output 0, phase frozen) but the voice is NOT disabled. Re-loading via a $4008 write resumes the voice without needing a fresh play event.

Default OFF: linearEnabled == false on construction, so the counter does not tick and the canonical track PCM is unchanged. Hito 2 M5.

Source: https://www.nesdev.org/wiki/APU_Linear_Counter