Add MMU bus arbiter

1 files changed, 86 insertions, 0 deletions

diff --git a/rtl/core/mmu/mmu.sv b/rtl/core/mmu/mmu.sv
new file mode 100644
index 0000000..9d118c1
--- /dev/null
+++ b/rtl/core/mmu/mmu.sv
@@ -0,0 +1,86 @@
+module core_mmu
+(
+	input  logic clk,
+
+	input  logic bus_ready,
+	input  word  bus_data_rd,
+	             data_data_wr,
+	input  ptr   insn_addr,
+	             data_addr,
+	input  logic insn_start,
+	             data_start,
+	             data_write,
+
+	output word  bus_data_wr,
+	output ptr   bus_addr,
+	output logic bus_start,
+	             bus_write,
+	             insn_ready,
+	             data_ready,
+	output word  insn_data_rd,
+	             data_data_rd
+);
+
+	enum
+	{
+		INSN,
+		DATA
+	} master, next_master;
+
+	//TODO
+	assign insn_data_rd = bus_data_rd;
+	assign data_data_rd = bus_data_rd;
+
+	always_comb begin
+		next_master = master;
+		if(bus_ready) begin
+			if(insn_start)
+				next_master = INSN;
+			else if(data_start)
+				next_master = DATA;
+		end
+
+		insn_ready = 0;
+		data_ready = 0;
+
+		unique case(master)
+			INSN: insn_ready = bus_ready;
+			DATA: data_ready = bus_ready;
+		endcase
+
+		unique case(next_master)
+			INSN: begin
+				bus_addr = insn_addr;
+				bus_data_wr = {32{1'bx}};
+			end
+
+			DATA: begin
+				bus_addr = data_addr;
+				bus_data_wr = data_data_wr;
+			end
+		endcase
+	end
+
+	always @(posedge clk) begin
+		master <= next_master;
+
+		unique case(next_master)
+			INSN: begin
+				bus_start <= insn_start;
+				bus_write <= 0;
+			end
+
+			DATA: begin
+				bus_start <= data_start;
+				bus_write <= data_write;
+			end
+		endcase
+	end
+
+	initial begin
+		master = INSN;
+		bus_start = 0;
+		bus_write = 0;
+	end
+
+endmodule