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module control_unit (
input clk,
input rstn,
input [31:0] instr,
input alu_zero,
output reg [2:0] imm_src,
output pc_we,
output reg mem_addr_src,
output reg mem_we,
output reg instr_we,
output reg [1:0] result_src,
output [3:0] alu_op,
output reg [1:0] alu_a_src,
output reg [1:0] alu_b_src,
output reg rf_we
);
parameter s00_fetch = 4'h0,
s01_decode = 4'h1,
s02_mem_addr = 4'h2,
s03_mem_read = 4'h3,
s04_mem_wb = 4'h4,
s05_mem_write = 4'h5,
s06_execute_r = 4'h6,
s07_alu_wb = 4'h7,
s08_execute_i = 4'h8,
s09_jal = 4'h9,
s10_jalr = 4'ha,
s11_br = 4'hb;
parameter INSTRUCTION_FORMAT_UNKNOWN = 3'b000,
INSTRUCTION_FORMAT_R = 3'b001,
INSTRUCTION_FORMAT_I = 3'b010,
INSTRUCTION_FORMAT_S = 3'b011,
INSTRUCTION_FORMAT_B = 3'b100,
INSTRUCTION_FORMAT_U = 3'b101,
INSTRUCTION_FORMAT_J = 3'b110;
wire [6:0] opcode;
wire [2:0] funct3;
wire [6:0] funct7;
assign opcode = instr[6:0];
assign funct3 = instr[14:12];
assign funct7 = instr[31:25];
always @ (*) begin
case (opcode)
7'b0110011: imm_src <= INSTRUCTION_FORMAT_R; // ADD, SUB, SLL, SLT, SLTU, XOR, SRL, SRA, OR, AND
7'b0010011: imm_src <= INSTRUCTION_FORMAT_I; // ADDI, SLTI, SLTIU, XORI, ORI, ANDI, SLLI, SRLI, SRAI
7'b0000011: imm_src <= INSTRUCTION_FORMAT_I; // LB, LH, LW, LBU, LHU
7'b1100111: imm_src <= INSTRUCTION_FORMAT_I; // JALR
7'b0100011: imm_src <= INSTRUCTION_FORMAT_S; // SB, SH, SW
7'b1100011: imm_src <= INSTRUCTION_FORMAT_B; // BEQ, BNE, BLT, BGE, BLTU, BGEU
7'b0110111: imm_src <= INSTRUCTION_FORMAT_U; // LUI
7'b0010111: imm_src <= INSTRUCTION_FORMAT_U; // AUIPC
7'b1101111: imm_src <= INSTRUCTION_FORMAT_J; // JAL
7'b0001111: imm_src <= INSTRUCTION_FORMAT_I; // FENCE, FENCE.I
7'b1110011: imm_src <= INSTRUCTION_FORMAT_I; // ECALL, EBREAK, CSRRW, CSRRS, CSRRC, CSRRWI, CSRRSI, CSRRCI
default: imm_src <= INSTRUCTION_FORMAT_UNKNOWN;
endcase
end
reg [3:0] state, next_state;
always @ (posedge clk) begin
if (!rstn) state <= s00_fetch;
else state <= next_state;
end
always @ (*) begin
case(state)
s00_fetch: next_state <= s01_decode;
s01_decode: case(opcode)
7'b0000011: next_state <= s02_mem_addr;
7'b0100011: next_state <= s02_mem_addr;
7'b0110011: next_state <= s06_execute_r;
7'b0010011: next_state <= s08_execute_i;
7'b1101111: next_state <= s09_jal;
7'b1100111: next_state <= s10_jalr;
7'b1100011: next_state <= s11_br;
default: next_state <= s00_fetch;
endcase
s02_mem_addr: case(opcode)
7'b0000011: next_state <= s03_mem_read;
7'b0100011: next_state <= s05_mem_write;
default: next_state <= s00_fetch;
endcase
s03_mem_read: next_state <= s04_mem_wb;
s04_mem_wb: next_state <= s00_fetch;
s05_mem_write: next_state <= s00_fetch;
s06_execute_r: next_state <= s07_alu_wb;
s07_alu_wb: next_state <= s00_fetch;
s08_execute_i: next_state <= s07_alu_wb;
s09_jal: next_state <= s07_alu_wb;
s10_jalr: next_state <= s07_alu_wb;
s11_br: next_state <= s00_fetch;
default: next_state <= s00_fetch;
endcase
end
reg branch;
reg pc_update;
reg alu_ctrl;
assign pc_we = ((alu_zero ^ funct3[0] ^ funct3[2]) & branch) | pc_update;
always @ (*) begin
case(state)
s00_fetch: begin
mem_addr_src <= 1'b0;
alu_a_src <= 2'b00;
alu_b_src <= 2'b10;
alu_ctrl <= 1'b1;
result_src <= 2'b10;
mem_we <= 1'b0;
rf_we <= 1'b0;
instr_we <= 1'b1;
pc_update <= 1'b1;
branch <= 1'b0;
end
s01_decode: begin
mem_addr_src <= 1'b0;
alu_a_src <= 2'b01;
alu_b_src <= 2'b01;
alu_ctrl <= 1'b1;
result_src <= 2'b00;
mem_we <= 1'b0;
rf_we <= 1'b0;
instr_we <= 1'b0;
pc_update <= 1'b0;
branch <= 1'b0;
end
s02_mem_addr: begin
mem_addr_src <= 1'b0;
alu_a_src <= 2'b10;
alu_b_src <= 2'b01;
alu_ctrl <= 1'b1;
result_src <= 2'b00;
mem_we <= 1'b0;
rf_we <= 1'b0;
instr_we <= 1'b0;
pc_update <= 1'b0;
branch <= 1'b0;
end
s03_mem_read: begin
mem_addr_src <= 1'b1;
alu_a_src <= 2'b00;
alu_b_src <= 2'b00;
alu_ctrl <= 1'b0;
result_src <= 2'b00;
mem_we <= 1'b0;
rf_we <= 1'b0;
instr_we <= 1'b0;
pc_update <= 1'b0;
branch <= 1'b0;
end
s04_mem_wb: begin
mem_addr_src <= 1'b0;
alu_a_src <= 2'b00;
alu_b_src <= 2'b00;
alu_ctrl <= 1'b0;
result_src <= 2'b01;
mem_we <= 1'b0;
rf_we <= 1'b1;
instr_we <= 1'b0;
pc_update <= 1'b0;
branch <= 1'b0;
end
s05_mem_write: begin
mem_addr_src <= 1'b1;
alu_a_src <= 2'b00;
alu_b_src <= 2'b00;
alu_ctrl <= 1'b0;
result_src <= 2'b00;
mem_we <= 1'b1;
rf_we <= 1'b0;
instr_we <= 1'b0;
pc_update <= 1'b0;
branch <= 1'b0;
end
s06_execute_r: begin
mem_addr_src <= 1'b0;
alu_a_src <= 2'b10;
alu_b_src <= 2'b00;
alu_ctrl <= 1'b0;
result_src <= 2'b00;
mem_we <= 1'b0;
rf_we <= 1'b0;
instr_we <= 1'b0;
pc_update <= 1'b0;
branch <= 1'b0;
end
s07_alu_wb: begin
mem_addr_src <= 1'b0;
alu_a_src <= 2'b00;
alu_b_src <= 2'b00;
alu_ctrl <= 1'b0;
result_src <= 2'b00;
mem_we <= 1'b0;
rf_we <= 1'b1;
instr_we <= 1'b0;
pc_update <= 1'b0;
branch <= 1'b0;
end
s08_execute_i: begin
mem_addr_src <= 1'b0;
alu_a_src <= 2'b10;
alu_b_src <= 2'b01;
alu_ctrl <= 1'b0;
result_src <= 2'b00;
mem_we <= 1'b0;
rf_we <= 1'b0;
instr_we <= 1'b0;
pc_update <= 1'b0;
branch <= 1'b0;
end
s09_jal: begin
mem_addr_src <= 1'b0;
alu_a_src <= 2'b01;
alu_b_src <= 2'b10;
alu_ctrl <= 1'b1;
result_src <= 2'b00;
mem_we <= 1'b0;
rf_we <= 1'b0;
instr_we <= 1'b0;
pc_update <= 1'b1;
branch <= 1'b0;
end
s10_jalr: begin
mem_addr_src <= 1'b0;
alu_a_src <= 2'b10;
alu_b_src <= 2'b01;
alu_ctrl <= 1'b1;
result_src <= 2'b10;
mem_we <= 1'b0;
rf_we <= 1'b0;
instr_we <= 1'b0;
pc_update <= 1'b1;
branch <= 1'b0;
end
s11_br: begin
mem_addr_src <= 1'b0;
alu_a_src <= 2'b10;
alu_b_src <= 2'b00;
alu_ctrl <= 1'b0;
result_src <= 2'b00;
mem_we <= 1'b0;
rf_we <= 1'b0;
instr_we <= 1'b0;
pc_update <= 1'b0;
branch <= 1'b1;
end
default: begin
mem_addr_src <= 1'b0;
alu_a_src <= 2'b00;
alu_b_src <= 2'b00;
alu_ctrl <= 1'b0;
result_src <= 2'b00;
mem_we <= 1'b0;
rf_we <= 1'b0;
instr_we <= 1'b0;
pc_update <= 1'b0;
branch <= 1'b0;
end
endcase
end
alu_op_decode aod (
.opcode(opcode),
.alu_ctrl(alu_ctrl),
.funct3(funct3),
.funct7(funct7),
.alu_op(alu_op)
);
endmodule
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