Attempt some basic voice details.

Analyser/Static/Acorn/Target.hpp

@@ -44,7 +44,7 @@ struct BBCMicroTarget: public ::Analyser::Static::Target, public Reflection::Str
 	bool has_1770dfs = false;
 	bool has_adfs = false;
 	bool has_sideways_ram = true;
-	bool has_beebsid = true;
+	bool has_beebsid = true;			// TODO: false is a much better default.
 
 	ReflectableEnum(TubeProcessor, None, WDC65C02, Z80);
 	TubeProcessor tube_processor = TubeProcessor::None;

Components/SID/SID.cpp

@@ -12,6 +12,30 @@ using namespace MOS::SID;
 
 SID::SID(Concurrency::AsyncTaskQueue<false> &audio_queue) : audio_queue_(audio_queue) {}
 
+
+void SID::write(const Numeric::SizedInt<5> address, const uint8_t value) {
+	switch(address.get()) {
+		case 0x00:	case 0x07:	case 0x0e:	voices_[address.get() / 7].frequency.load<0>(value);	break;
+		case 0x01:	case 0x08:	case 0x0f:	voices_[address.get() / 7].frequency.load<8>(value);	break;
+		case 0x02:	case 0x09:	case 0x10:	voices_[address.get() / 7].pulse_width.load<0>(value);	break;
+		case 0x03:	case 0x0a:	case 0x11:	voices_[address.get() / 7].pulse_width.load<8>(value);	break;
+		case 0x04:	case 0x0b:	case 0x12:	voices_[address.get() / 7].control = value;				break;
+		case 0x05:	case 0x0c:	case 0x13:
+			voices_[address.get() / 7].attack = value >> 4;
+			voices_[address.get() / 7].decay = value;
+		break;
+		case 0x06:	case 0x0d:	case 0x14:
+			voices_[address.get() / 7].sustain = value >> 4;
+			voices_[address.get() / 7].release = value;
+		break;
+	}
+}
+
+uint8_t SID::read(const Numeric::SizedInt<5> address) {
+	(void)address;
+	return 0xff;
+}
+
 void SID::set_sample_volume_range(const std::int16_t range) {
 	(void)range;
 }

Components/SID/SID.hpp

@@ -8,6 +8,8 @@
 
 #pragma once
 
+#include "Numeric/SizedInt.hpp"
+
 #include "Concurrency/AsyncTaskQueue.hpp"
 #include "Outputs/Speaker/Implementation/BufferSource.hpp"
 
@@ -17,6 +19,10 @@ class SID: public Outputs::Speaker::BufferSource<SID, false> {
 public:
 	SID(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
+	void write(Numeric::SizedInt<5> address, uint8_t value);
+	uint8_t read(Numeric::SizedInt<5> address);
+
+	// Outputs::Speaker::BufferSource.
 	template <Outputs::Speaker::Action action>
 		void apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target);
 	bool is_zero_level() const;
@@ -24,6 +30,18 @@ public:
 
 private:
 	Concurrency::AsyncTaskQueue<false> &audio_queue_;
+
+	struct Voice {
+		Numeric::SizedInt<16> frequency;
+		Numeric::SizedInt<12> pulse_width;
+		Numeric::SizedInt<8> control;
+		Numeric::SizedInt<4> attack;
+		Numeric::SizedInt<4> decay;
+		Numeric::SizedInt<4> sustain;
+		Numeric::SizedInt<4> release;
+	};
+
+	Voice voices_[3];
 };
 
 }

Machines/Acorn/BBCMicro/BBCMicro.cpp

@@ -109,6 +109,8 @@ private:
 /*!
 	Combines an SN76489 with an appropriate asynchronous queue and filtering speaker.
 */
+
+// TODO: generalise the below and clean up across the project.
 template <bool has_beebsid>
 struct Audio {
 private:
@@ -147,7 +149,7 @@ public:
 			return sn76489_;
 		}
 		if constexpr (std::is_same_v<TargetT, MOS::SID::SID>) {
-			return sn76489_;
+			return sid_;
 		}
 	}
 
@@ -1027,6 +1029,12 @@ public:
 						}
 					break;
 				}
+			} else if(has_beebsid && address >= 0xfc20 && address < 0xfc40) {
+				if constexpr (is_read(operation)) {
+					value = audio_.template get<MOS::SID::SID>().read(+address);
+				} else {
+					audio_.template get<MOS::SID::SID>().write(+address, value);
+				}
 			} else {
 				Logger::error()
 					.append("Unhandled IO %s at %04x", is_read(operation) ? "read" : "write", address)