1 files changed, 94 insertions, 0 deletions
diff --git a/src/cpu.sv b/src/cpu.sv
new file mode 100644
index 0000000..0efcd6d
--- /dev/null
+++ b/src/cpu.sv
@@ -0,0 +1,94 @@
+module cpu(clk, reset, mem_data, mem_cmd, mem_addr, out, N, V, Z, halt);
+	input clk, reset;
+	input [15:0] mem_data;
+	output N, V, Z, halt;
+	output [1:0] mem_cmd;
+	output [15:0] out;
+	output reg [8:0] mem_addr;
+
+	wire pc_reset, pc_load, ir_load, addr_sel, write, loada, loadb, loadc,
+		loads, loadm, asel, bsel, csel;
+	wire [1:0] pc_sel, op, sh;
+	wire [2:0] opcode, cond, Rn, Rd, Rm, reg_w_sel, reg_a_sel, reg_b_sel;
+	wire [3:0] vsel;
+	wire [8:0] PC, data_address;
+	wire [15:0] instruction, sximm5, sximm8;
+	reg [2:0] reg_w, reg_a, reg_b;
+	reg [8:0] pc_next;
+
+	register #(16) U0(mem_data, ir_load, clk, instruction);
+	register #(9) U1(pc_next, pc_load, clk, PC);
+
+	statemachine FSM(clk, reset, opcode, op, pc_reset, pc_load, pc_sel,
+		ir_load, addr_sel, mem_cmd, reg_w_sel, reg_a_sel,
+		reg_b_sel, write, loada, loadb, loadc, loads, loadm, asel, bsel,
+		csel, vsel, halt);
+
+	datapath DP(clk, reg_w, reg_a, reg_b, write, loada, loadb, loadc, loads,
+		loadm, op, sh, asel, bsel, csel, vsel, sximm5, sximm8,
+		mem_data, PC, N, V, Z, out, data_address);
+
+	assign mem_addr = addr_sel ? PC : data_address;
+
+	/* Instruction decoder. */
+	assign {opcode, op, Rn, Rd, sh, Rm} = instruction;
+	assign cond = instruction[10:8];
+	assign sximm8 = {{8{instruction[7]}}, instruction[7:0]};
+	assign sximm5 = {{11{instruction[4]}}, instruction[4:0]};
+
+	always_comb begin
+		/* Selector for REGFILE read/write registers. */
+		case (reg_w_sel)
+		3'b100: reg_w = Rn;
+		3'b010: reg_w = Rd;
+		3'b001: reg_w = Rm;
+		default: reg_w = 3'bzzz;
+		endcase
+		case (reg_a_sel)
+		3'b100: reg_a = Rn;
+		3'b010: reg_a = Rd;
+		3'b001: reg_a = Rm;
+		default: reg_a = 3'bzzz;
+		endcase
+		case (reg_b_sel)
+		3'b100: reg_b = Rn;
+		3'b010: reg_b = Rd;
+		3'b001: reg_b = Rm;
+		default: reg_b = 3'bzzz;
+		endcase
+
+		/* Branching logic. */
+		casex ({pc_reset, pc_sel})
+		3'b1_xx:
+			pc_next = 9'b0;
+		3'b0_01: begin
+			pc_next = PC;
+			case ({opcode, cond})
+			/* B. */
+			6'b001_000:
+				pc_next = PC + sximm8[8:0];
+			/* BEQ. */
+			6'b001_001: if (Z)
+				pc_next = PC + sximm8[8:0];
+			/* BNE. */
+			6'b001_010: if (~Z)
+				pc_next = PC + sximm8[8:0];
+			/* BLT. */
+			6'b001_011: if (N !== V)
+				pc_next = PC + sximm8[8:0];
+			/* BLE. */
+			6'b001_100: if (N !== V | Z)
+				pc_next = PC + sximm8[8:0];
+			endcase
+		end
+		/* BX, BLX. */
+		3'b0_10:
+			pc_next = out;
+		/* BL. */
+		3'b0_11:
+			pc_next = PC + sximm8[8:0];
+		/* Next address in memory. */
+		default: pc_next = PC + 1;
+		endcase
+	end
+endmodule: cpu