From 54544911601351465a6a887a045f3baddcb90dc6 Mon Sep 17 00:00:00 2001
From: Alejandro Soto <alejandro@34project.org>
Date: Sun, 18 Sep 2022 17:14:54 -0600
Subject: Implement Avalon memory module for simulation

---
 tb/mem.cpp | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 tb/mem.hpp | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 85 insertions(+)
 create mode 100644 tb/mem.cpp
 create mode 100644 tb/mem.hpp

(limited to 'tb')

diff --git a/tb/mem.cpp b/tb/mem.cpp
new file mode 100644
index 0000000..bfbc3ea
--- /dev/null
+++ b/tb/mem.cpp
@@ -0,0 +1,49 @@
+#include <cassert>
+#include <cstdint>
+#include <memory>
+
+#include "mem.hpp"
+
+namespace taller::avalon
+{
+	mem::mem(std::uint32_t base, std::uint32_t size)
+	: base(base), mask(~(size - 1)),
+	  block(std::make_unique<std::uint32_t[]>(size >> 2))
+	{
+		assert(!(size & 0b11) && !((size - 1) & size));
+	}
+
+	bool mem::read(std::uint32_t addr, std::uint32_t &data)
+	{
+		data = block[addr];
+		return true;
+	}
+
+	bool mem::write(std::uint32_t addr, std::uint32_t data, unsigned byte_enable)
+	{
+		std::uint32_t bytes = 0;
+
+		if(byte_enable & 0b1000)
+		{
+			bytes |= 0xff << 24;
+		}
+
+		if(byte_enable & 0b0100)
+		{
+			bytes |= 0xff << 16;
+		}
+
+		if(byte_enable & 0b0010)
+		{
+			bytes |= 0xff << 8;
+		}
+
+		if(byte_enable & 0b0001)
+		{
+			bytes |= 0xff;
+		}
+
+		block[addr] = (data & bytes) | (block[addr] & ~bytes);
+		return true;
+	}
+}
diff --git a/tb/mem.hpp b/tb/mem.hpp
new file mode 100644
index 0000000..0d9bbb0
--- /dev/null
+++ b/tb/mem.hpp
@@ -0,0 +1,36 @@
+#ifndef MEM_HPP
+#define MEM_HPP
+
+#include <cstdint>
+#include <memory>
+
+#include "avalon.hpp"
+
+namespace taller::avalon
+{
+	class mem : public slave
+	{
+		public:
+			mem(std::uint32_t base, std::uint32_t size);
+
+			virtual inline std::uint32_t base_address() noexcept final override
+			{
+				return base;
+			}
+
+			virtual inline std::uint32_t address_mask() noexcept final override
+			{
+				return mask;
+			}
+
+			virtual bool read(std::uint32_t addr, std::uint32_t &data);
+			virtual bool write(std::uint32_t addr, std::uint32_t data, unsigned byte_enable);
+
+		private:
+			std::unique_ptr<std::uint32_t[]> block;
+			std::uint32_t                    base;
+			std::uint32_t                    mask;
+	};
+}
+
+#endif
-- 
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