Start transferring 6502 precepts.

OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj

@@ -1801,6 +1801,7 @@
 		4B882F582C2F9C6900D84031 /* CPCShakerTests.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = CPCShakerTests.mm; sourceTree = "<group>"; };
 		4B882F5A2C2F9C7700D84031 /* Shaker */ = {isa = PBXFileReference; lastKnownFileType = folder; path = Shaker; sourceTree = "<group>"; };
 		4B884C6F2EA28E0F00073840 /* CompileTimeCounter.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = CompileTimeCounter.hpp; sourceTree = "<group>"; };
+		4B884C722EA47FCC00073840 /* 6502Mk2.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = 6502Mk2.hpp; sourceTree = "<group>"; };
 		4B88559C2E8185BF00E251DD /* SizedInt.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = SizedInt.hpp; sourceTree = "<group>"; };
 		4B8855A22E84D51B00E251DD /* SAA5050.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = SAA5050.hpp; sourceTree = "<group>"; };
 		4B8855A32E84D51B00E251DD /* SAA5050.cpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; path = SAA5050.cpp; sourceTree = "<group>"; };
@@ -3859,6 +3860,14 @@
 			path = Data;
 			sourceTree = "<group>";
 		};
+		4B884C732EA47FCC00073840 /* 6502Mk2 */ = {
+			isa = PBXGroup;
+			children = (
+				4B884C722EA47FCC00073840 /* 6502Mk2.hpp */,
+			);
+			path = 6502Mk2;
+			sourceTree = "<group>";
+		};
 		4B8855A42E84D51B00E251DD /* SAA5050 */ = {
 			isa = PBXGroup;
 			children = (
@@ -4900,6 +4909,7 @@
 				4BFCA1221ECBDCAF00AC40C1 /* AllRAMProcessor.hpp */,
 				4B1414561B58879D00E04248 /* 6502 */,
 				4B4DEC15252BFA9C004583AC /* 6502Esque */,
+				4B884C732EA47FCC00073840 /* 6502Mk2 */,
 				4BF8D4CC251C0C9C00BBE21B /* 65816 */,
 				42AD552D2A0C4D5000ACE410 /* 68000 */,
 				4B77069E1EC9045B0053B588 /* Z80 */,

Processors/6502Mk2/6502Mk2.hpp

@@ -0,0 +1,170 @@
+//
+//  6502Mk2.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 18/10/2025.
+//  Copyright © 2025 Thomas Harte. All rights reserved.
+//
+
+#pragma once
+
+namespace CPU::MOS6502Mk2 {
+
+// MARK: - Address resolvers.
+
+namespace Address {
+
+struct Literal {
+	constexpr LiteralAddress(const uint16_t address) noexcept : address_(address);
+	operator uint16_t() const {
+		return address_;
+	}
+
+private:
+	uint16_t address_;
+};
+
+struct ZeroPage {
+	constexpr ZeroPage(const uint8_t address) noexcept : address_(address);
+	operator uint16_t() const {
+		return address_;
+	}
+
+private:
+	uint8_t address_;
+};
+
+struct Stack {
+	constexpr ZeroPage(const uint8_t address) noexcept : address_(address);
+	operator uint16_t() const {
+		return 0x0100 | address_;
+	}
+
+private:
+	uint8_t address_;
+};
+
+struct Vector {
+	constexpr ZeroPage(const uint8_t address) noexcept : address_(address);
+	operator uint16_t() const {
+		return 0xff00 | address_;
+	}
+
+private:
+	uint8_t address_;
+};
+
+}  // namespace Address
+
+namespace Data {
+
+struct NoValue {
+	operator uint8_t() const { return 0xff; }
+};
+
+/*!
+	Bus handlers perform bus transactions, connecting the 6502-esque chip to the rest of the syste.
+	@c BusOperation provides the type of operation.
+*/
+enum class BusOperation {
+	/// 6502: a read was signalled.
+	/// 65816: a read was signalled with VDA.
+	Read,
+	/// 6502: a read was signalled with SYNC.
+	/// 65816: a read was signalled with VDA and VPA.
+	ReadOpcode,
+	/// 6502: never signalled.
+	/// 65816: a read was signalled with VPA.
+	ReadProgram,
+	/// 6502: never signalled.
+	/// 65816: a read was signalled with VPB and VDA.
+	ReadVector,
+	/// 6502: never signalled.
+	/// 65816: a read was signalled, but neither VDA nor VPA were active.
+	InternalOperationRead,
+
+	/// All processors: indicates that the processor is paused due to the RDY input.
+	/// 65C02 and 65816: indicates a WAI is ongoing.
+	Ready,
+
+	/// 65C02 and 65816: indicates a STP condition.
+	None,
+
+	/// 6502: a write was signalled.
+	/// 65816: a write was signalled with VDA.
+	Write,
+	/// 6502: never signalled.
+	/// 65816: a write was signalled, but neither VDA nor VPA were active.
+	InternalOperationWrite,
+};
+
+constexpr bool is_read(const BusOperation op) { return op <= BusOperation::InternalOperationRead; }
+constexpr bool is_write(const BusOperation op) { return op >= BusOperation::Write; }
+constexpr bool is_access(const BusOperation op) { return op <= BusOperation::ReadVector || op == BusOperation::Write; }
+constexpr bool is_dataless(const BusOperation op) { return !is_read(op) && !is_write(op); }
+
+template <BusOperation, typename Enable = void> struct Value;
+template <BusOperation operation> struct Value<operation, std::enable_if_t<is_read(operation)> {
+	using type = uint8_t &;
+};
+template <BusOperation operation> struct Value<operation, std::enable_if_t<is_write(operation)> {
+	using type = const uint8_t;
+};
+template <BusOperation operation> struct Value<operation, std::enable_if_t<is_dataless(operation)> {
+	using type = const NoValue;
+};
+
+} // namespace Data
+
+/*
+	The list of registers that can be accessed via @c value_of(Register) and @c set_value_of(Register, value).
+*/
+enum class Register {
+	LastOperationAddress,
+	ProgramCounter,
+	StackPointer,
+	Flags,
+	A,
+	X,
+	Y,
+
+	//
+	// 65816 only.
+	//
+	EmulationFlag,
+	DataBank,
+	ProgramBank,
+	Direct
+};
+
+/*
+	Flags as defined on the 6502; can be used to decode the result of @c value_of(Flags) or to form a value for
+	the corresponding set.
+*/
+enum Flag: uint8_t {
+	Sign		= 0b1000'0000,
+	Overflow	= 0b0100'0000,
+	Always		= 0b0010'0000,
+	Break		= 0b0001'0000,
+	Decimal		= 0b0000'1000,
+	Interrupt	= 0b0000'0100,
+	Zero		= 0b0000'0010,
+	Carry		= 0b0000'0001,
+
+	//
+	// 65816 only.
+	//
+	MemorySize	= Always,
+	IndexSize	= Break,
+};
+
+enum Personality {
+	PNES6502,			// The NES's 6502; like a 6502 but lacking decimal mode (though it retains the decimal flag).
+	P6502,				// NMOS 6502.
+	PSynertek65C02,		// A 6502 extended with BRA, P[H/L][X/Y], STZ, TRB, TSB and the (zp) addressing mode, and more.
+	PRockwell65C02,		// The Synertek extended with BBR, BBS, RMB and SMB.
+	PWDC65C02,			// The Rockwell extended with STP and WAI.
+	P65816,				// The "16-bit" successor to the 6502.
+};
+
+}