diff --git a/rtl/decoder.v b/rtl/decoder.v
index 9312975..dba0a96 100644
--- a/rtl/decoder.v
+++ b/rtl/decoder.v
@@ -12,12 +12,12 @@ module decoder (input [31:0] instruction,
 function [3:0] get_op_code_alu(input [2:0] op_code, input arithmetic);
     begin
         case (op_code)
-            3'b000 : get_op_code_alu = arithmetic ? 4'b0000 : 4'b0001;
+            3'b000 : get_op_code_alu = arithmetic ? 4'b0001 : 4'b0000;
             3'b001 : get_op_code_alu = 4'b0010;
             3'b010 : get_op_code_alu = 4'b0011;
             3'b011 : get_op_code_alu = 4'b0011;
             3'b100 : get_op_code_alu = 4'b0100;
-            3'b101 : get_op_code_alu = arithmetic ? 4'b0101 : 4'b0111;
+            3'b101 : get_op_code_alu = arithmetic ? 4'b0111 : 4'b0101;
             3'b110 : get_op_code_alu = 4'b1000;
             3'b111 : get_op_code_alu = 4'b1010;
             3'b111 : get_op_code_alu = 4'b1011;
@@ -34,7 +34,7 @@ function [3:0] get_op_code_alu_imm(input [2:0] op_code, input arithmetic);
             3'b010 : get_op_code_alu_imm = 4'b0011;
             3'b011 : get_op_code_alu_imm = 4'b0100;
             3'b100 : get_op_code_alu_imm = 4'b0101;
-            3'b101 : get_op_code_alu_imm = arithmetic ? 4'b0111 : 4'b1000;
+            3'b101 : get_op_code_alu_imm = arithmetic ? 4'b1000 : 4'b0111;
             3'b110 : get_op_code_alu_imm = 4'b1001;
             3'b111 : get_op_code_alu_imm = 4'b1010;
             3'b111 : get_op_code_alu_imm = 4'b1011;
@@ -94,7 +94,8 @@ endfunction
                 alu_not = 0;
             end
             5'b00100 : begin // OP-IMM - Addi, ...
-                immediate = instruction[31:20];
+                immediate[11:0] = instruction[31:20];
+                immediate[31:12] = (instruction[14:12] == 3'b011 || instruction[31] == 0) ? 12'b00000000000000000000 : 12'b11111111111111111111;
                 we_reg = 1;
                 adder_pc = 0;
                 data_out = 0;
@@ -110,7 +111,8 @@ endfunction
                 alu_not = 0;
             end
             5'b00000 : begin // LOAD - Lw, ...
-                immediate = instruction[31:20];
+                immediate[11:0] = instruction[31:20];
+                immediate[31:12] = (instruction[14:12] == 3'b100 || instruction[14:12] == 3'b101 || instruction[31] == 0) ? 12'b00000000000000000000 : 12'b11111111111111111111;
                 we_reg = 1;
                 adder_pc = 0;
                 data_out = 0;
@@ -126,7 +128,8 @@ endfunction
                 alu_not = 0;
             end
             5'b01000 : begin // STORE - Sw, ...
-                immediate = {instruction[31:25], instruction[11:7]};
+                immediate[11:0] = {instruction[31:25], instruction[11:7]};
+                immediate[31:12] = (instruction[31] == 0) ? 12'b00000000000000000000 : 12'b11111111111111111111;
                 we_reg = 0;
                 adder_pc = 0;
                 data_out = 0;
@@ -142,7 +145,8 @@ endfunction
                 alu_not = 0;
             end
             5'b11000 : begin // BRANCH - Beq, ...
-                immediate = {instruction[31:25], instruction[11:7]};
+                immediate[11:0] = {instruction[31:25], instruction[11:7]};
+                immediate[31:12] = (instruction[14:12] == 3'b110 || instruction[14:12] == 3'b111 || instruction[31] == 0) ? 12'b00000000000000000000 : 12'b11111111111111111111;
                 we_reg = 0;
                 adder_pc = 0;
                 data_out = 0;
@@ -158,7 +162,8 @@ endfunction
                 alu_not = branch_not(instruction[14:12]);
             end
             5'b11011 : begin // JUMP - Jal
-                immediate = instruction[31:12];
+                immediate[19:0] = instruction[31:12];
+                immediate[31:20] = (instruction[31] == 0) ? 12'b000000000000 : 12'b111111111111;
                 we_reg = 1;
                 adder_pc = 0;
                 data_out = 0;
@@ -174,7 +179,8 @@ endfunction
                 alu_not = 0;
             end
             5'b11001 : begin // JUMP REG - Jalr
-                immediate = instruction[31:20];
+                immediate[19:0] = instruction[31:12];
+                immediate[31:20] = (instruction[31] == 0) ? 12'b000000000000 : 12'b111111111111;
                 we_reg = 1;
                 adder_pc = 0;
                 data_out = 0;
@@ -190,7 +196,7 @@ endfunction
                 alu_not = 0;
             end
             5'b01101 : begin // LUI - lui
-                immediate = instruction[31:12] << 12;
+                immediate = {instruction[31:12] << 12, 12'b000000000000};
                 we_reg = 1;
                 adder_pc = 0;
                 data_out = 1;
@@ -206,7 +212,7 @@ endfunction
                 alu_not = 0;
             end
             5'b00101 : begin // AUIPC - auipc
-                immediate = instruction[31:12] << 12;
+                immediate = {instruction[31:12] << 12, 12'b000000000000};
                 we_reg = 1;
                 adder_pc = 1;
                 data_out = 1;
diff --git a/rtl/instruction.v b/rtl/instruction.v
index fd3d125..8ac4e87 100644
--- a/rtl/instruction.v
+++ b/rtl/instruction.v
@@ -3,29 +3,29 @@ module instruction (input [31:0] address,
     
     reg [31:0] memory [63:0];
 
-    // ADDi $1, R[0], R[6]
+    // ADDi $1, R[0], R[6] - R[6] = 1
     // "000000000001_00000_000_00110_0010000"
     assign memory[0] = 32'b00000000000100000000001100010000;
 
-    // ADDi $0, R[0], R[7]
+    // ADDi $0, R[0], R[7] - R[7] = 0
     // "000000000000_00000_000_00111_0010000"
     assign memory[4] = 32'b00000000000000000000001110010000;
 
-    // ADDi $0, R[6],  R[8]
+    // ADDi $0, R[6],  R[8] - R[8] = R[6]
     // "000000000000_00110_000_01000_0010000"
     assign memory[8] = 32'b00000000000000110000010000010000;
 
-    // ADD R[7], R[6], R[6]
+    // ADD R[7], R[6], R[6] - R[6] = R[7] + R[6]
     // "0000000_00111_00110_000_00110_0110000"
     assign memory[12] = 32'b00000000011100110000001100110000;
 
-    // ADDi $0, R[8], R[7]
+    // ADDi $0, R[8], R[7] - R[7] = R[8]
     // "000000000000_01000_000_00111_0010000"
     assign memory[16] = 32'b00000000000001000000001110010000;
 
     // JUMP 
-    // 111111111111_11111_101_00111_1101100
-    assign memory[20] = 32'b11111111111111111101001111101100;
+    // 11111111111111111101_00111_1101100
+    assign memory[20] = 32'b11111111111111110100001011101100;
 
     assign instruction = memory[address];