riscv single cycle

chapter4/RISCcore.v

@@ -0,0 +1,133 @@
+module RISCcore (
+  input rst,
+  input clk,
+  output reg [31:0] pc,
+  output reg [31:0] next_pc,
+  output wire [31:0] instr
+);
+
+
+//PC
+always @(posedge clk) begin 
+  if(rst) begin
+    pc <= 32'h0;
+    next_pc <= 32'h4;
+  end
+  else begin 
+    next_pc <= taken_br ? br_tgt_pc : (pc + 32'h4);
+    pc <= next_pc;
+  end
+end
+
+//IMem
+reg [31:0] imem [0:255];
+
+initial begin
+  $readmemh("program.hex", imem);
+end
+
+assign instr = imem[pc[31:2]];
+
+//Decoder
+
+wire isUType = ((instr[6:0] == 7'b0110111) || (instr[6:0] == 7'b0010111));
+wire isIType = ((instr[6:0] == 7'b0000011) || (instr[6:0] == 7'b0000111) || (instr[6:0] == 7'b0010011) || (instr[6:0] == 7'b0011011) || (instr [6:0] == 7'b1100111));
+wire isRType = ((instr[6:0] == 7'b0101111) || (instr[6:0] == 7'b0110011) || (instr[6:0] == 7'b0111011) || (instr[6:0] == 7'b0110011));
+wire isSType = ((instr[6:0] == 7'b0100011) || (instr[6:0] == 7'b0100111));
+wire isBType = (instr[6:0] == 7'b1100011);
+wire isJType = (instr[6:0] == 7'b1101111);
+
+wire [4:0] rs1 = instr[19:15];
+wire [4:0] rs2 = instr[24:20];
+wire [4:0] rd = instr[11:7];
+
+wire rs2Valid = (isRType || isSType || isBType);
+wire rs1Valid = (~isUType && ~isJType);
+wire rdValid = (~isSType && ~isBType);
+
+wire [3:0] funct3 = instr[14:12];
+wire [6:0] funct7 = instr[31:25];
+
+wire funct3Valid = rs1Valid;
+wire funct7Valid = isRType;
+
+wire [31:0] Iimm = {{21{instr[31]}}, {instr[30:25]}, {instr[24:20]}};
+wire [31:0] Simm = {{21{instr[31]}}, {instr[30:25]}, {instr[11:7]}};
+wire [31:0] Bimm = {{20{instr[31]}}, {instr[7]}, {instr[30:25]}, {instr[11:8]}, 1'b0};
+wire [31:0] Uimm = {{instr[31]}, {instr[30:20]}, {instr[19:12]}, {12{1'b0}};
+wire [31:0] Jimm = {{12{instr[31]}}, {instr[19:12]}, {instr[20]}, {instr[30:25]}, {instr[24:21]}, 1'b0};
+
+//Instructions
+
+isBEQ = (funct3 == 3'b000 && isBType);
+isBNE = (funct3 == 3'b001 && isBType);
+isBLT = (funct3 == 3'b100 && isBType);
+isBGE = (funct3 == 3'b101 && isBType);
+isBLTU = (funct3 == 3'b110 && isBType);
+isBGEU = (funct3 == 3'b111 && isBType);
+
+isADDI = (funct3 == 3'b000 && isIType);
+
+isADD = (funct7[5] == 1'b0 && isRType);
+
+isLW = (funct3 == 3'b010 && isIType);
+isSW = (funct3 == 3'b010 && isSType);
+
+//Register file
+
+wire rf_wr_en;
+wire [4:0] rf_wr_index;
+wire [31:0] rf_wr_data;
+wire rf_rd_en1, rf_rd_en2;
+wire [4:0] rf_rd_index1, rf_rd_index2;
+
+wire rf_rd_data1, rf_rd_data2;
+
+wire src1_value, src2_value;
+
+assign rf_rd_en1 = rs1Valid;
+assign rf_rd_en2 = rs2Valid;
+
+assign rf_rd_index1 = rs1;
+assign rf_rd_index2 = rs2;
+
+assign [31:0] src1_value = {31{rf_rd_data1}};
+assign [31:0] src2_value = {31{rf_rd_data2}};
+
+/* Maybe write logic ?
+assign rf_wr_en = 1'b0;
+assign rf_wr_index = 5'b0;
+assign rf_wr_data = 32'b0;
+Disabled */
+
+// ALU FOR ADD, ADDI 
+wire [31:0] alu_result = 32'b0;
+wire [31:0] alu_op2 = isADDI ? Iimm : src2_value;
+
+assign alu_result = (isADDI || isADD) ? (src1_value + alu_op2) : 32'b0;
+
+//ALU Register file connect
+/*
+assign rf_wr_data = alu_result;
+assign rf_wr_en = rdValid && (isADD || isADDI);
+assign rf_wr_index = rd;
+*/
+
+//x0 support adding 
+assign rf_wr_data = rf_wr_en ? alu_result : 32'b0;
+assign rf_wr_en = rdValid && (isADD || isADDI) && (rd != 5'b0);
+assign rf_wr_index = rd;
+
+//Branch
+if(isBType) begin 
+  wire taken_br = (isBEQ ? src1_value == src2_value : 1'b0) ||
+    (isBNE ? src1_value != src2_value : 1'b0) ||
+    (isBLT ? ((src1_value < src2_value) ^ (src1_value[31] != src2_value[31])) : 1'b0) ||
+    (isBGE ? ((src1_value >= src2_value) ^ (src1_value[31] != src2_value)) : 1'b0) ||
+    (isBLTU ? src1_value < src2_value : 1'b0) ||
+    (isBGEU ? src1_value >= src2_value : 1'b0);
+  wire [31:0] br_tgt_pc = next_pc + Bimm;
+end 
+
+
+endmodule