From 387791635eafe1e9ed15a144dd1caef424146399 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Mon, 4 Mar 2024 21:43:06 -0500
Subject: [PATCH] Start to establish a memory map.

---
 Machines/Acorn/Archimedes/Archimedes.cpp | 61 +++++++++++++++++++++++-
 1 file changed, 60 insertions(+), 1 deletion(-)

diff --git a/Machines/Acorn/Archimedes/Archimedes.cpp b/Machines/Acorn/Archimedes/Archimedes.cpp
index a4c8fd0e8..bca5457e4 100644
--- a/Machines/Acorn/Archimedes/Archimedes.cpp
+++ b/Machines/Acorn/Archimedes/Archimedes.cpp
@@ -20,8 +20,44 @@
 #include <array>
 #include <vector>
 
+namespace {
+
+enum class Zone {
+	LogicallyMappedRAM,
+	PhysicallyMappedRAM,
+	IOControllers,
+	LowROM,
+	HighROM,
+	VideoController,
+	DMAAndMEMC,
+	AddressTranslator,
+};
+constexpr std::array<Zone, 0x20> zones(bool is_read) {
+	std::array<Zone, 0x20> zones{};
+	for(size_t c = 0; c < zones.size(); c++) {
+		const auto address = c << 21;
+		if(address < 0x200'0000) {
+			zones[c] = Zone::LogicallyMappedRAM;
+		} else if(address < 0x300'0000) {
+			zones[c] = Zone::PhysicallyMappedRAM;
+		} else if(address < 0x340'0000) {
+			zones[c] = Zone::IOControllers;
+		} else if(address < 0x360'0000) {
+			zones[c] = is_read ? Zone::LowROM : Zone::VideoController;
+		} else if(address < 0x380'0000) {
+			zones[c] = is_read ? Zone::LowROM : Zone::DMAAndMEMC;
+		} else {
+			zones[c] = is_read ? Zone::HighROM : Zone::AddressTranslator;
+		}
+	}
+	return zones;
+}
+
+}
+
 namespace Archimedes {
 
+/// Primarily models the MEMC.
 struct Memory {
 	void set_rom(const std::vector<uint8_t> &rom) {
 		std::copy(
@@ -35,7 +71,19 @@ struct Memory {
 		(void)mode;
 		(void)trans;
 
-		printf("W of %08x to %08x [%lu]\n", source, address, sizeof(IntT));
+		switch (write_zones_[(address >> 21) & 31]) {
+			case Zone::DMAAndMEMC:
+//				if(mode != InstructionSet::ARM::Mode::Supervisor) return false;
+				if((address & 0b1110'0000'0000'0000'0000) == 0b1110'0000'0000'0000'0000) {
+					printf("MEMC Control: %04x\n", source);
+					break;
+				}
+			[[fallthrough]];
+
+			default:
+				printf("Unhandled W of %08x to %08x [%lu]\n", source, address, sizeof(IntT));
+			break;
+		}
 
 		if(has_moved_rom_ && address < ram_.size()) {
 			*reinterpret_cast<IntT *>(&ram_[address]) = source;
@@ -49,6 +97,14 @@ struct Memory {
 		(void)mode;
 		(void)trans;
 
+		switch (read_zones_[(address >> 21) & 31]) {
+			case Zone::PhysicallyMappedRAM:
+//				if(mode != InstructionSet::ARM::Mode::Supervisor) return false;
+				source = *reinterpret_cast<const IntT *>(&ram_[address & (ram_.size() - 1)]);
+			return true;
+
+			default: break;
+		}
 		if(address >= 0x3800000) {
 			has_moved_rom_ = true;
 			source = *reinterpret_cast<const IntT *>(&rom_[address - 0x3800000]);
@@ -68,6 +124,9 @@ struct Memory {
 		bool has_moved_rom_ = false;
 		std::array<uint8_t, 4*1024*1024> ram_{};
 		std::array<uint8_t, 2*1024*1024> rom_;
+
+		static constexpr std::array<Zone, 0x20> read_zones_ = zones(true);
+		static constexpr std::array<Zone, 0x20> write_zones_ = zones(false);
 };
 
 class ConcreteMachine: