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fix(apu): resolve bug in NR10 obscure behaviour

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This commit is contained in:
Rekai Nyangadzayi Musuka
2022-12-05 11:08:04 -04:00
parent 240fbcb1df
commit bf95eee3f1
2 changed files with 7 additions and 6 deletions
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7
src/core/apu/ToneSweep.zig
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@@ -94,10 +94,9 @@ pub fn sound1CntL(self: *const Self) u8 {
pub fn setSound1CntL(self: *Self, value: u8) void {
const new = io.Sweep{ .raw = value };
if (self.sweep.direction.read() and !new.direction.read()) {
// Sweep Negate bit has been cleared
// If At least 1 Sweep Calculation has been made since
// the last trigger, the channel is immediately disabled
if (!new.direction.read()) {
// If at least one (1) sweep calculation has been made with
// the negate bit set (since last trigger), disable the channel
if (self.sweep_dev.calc_performed) self.enabled = false;
}

6
src/core/apu/device/Sweep.zig
View File

@@ -31,7 +31,6 @@ pub fn tick(self: *Self, ch1: *ToneSweep) void {
if (self.timer == 0) {
const period = ch1.sweep.period.read();
self.timer = if (period == 0) 8 else period;
if (!self.calc_performed) self.calc_performed = true;
if (self.enabled and period != 0) {
const new_freq = self.calculate(ch1.sweep, &ch1.enabled);
@@ -52,7 +51,10 @@ pub fn calculate(self: *Self, sweep: io.Sweep, ch_enable: *bool) u12 {
const shadow_shifted = shadow >> sweep.shift.read();
const decrease = sweep.direction.read();
const freq = if (decrease) shadow - shadow_shifted else shadow + shadow_shifted;
const freq = if (decrease) blk: {
self.calc_performed = true;
break :blk shadow - shadow_shifted;
} else shadow + shadow_shifted;
if (freq > 0x7FF) ch_enable.* = false;
return freq;