Improved instruction decoding

cpu/boot_code.asm

@@ -1,4 +1,4 @@
-ADD AX,#0x55AA
-ADD CX,#0xEFBE
-ADD CX,#0x1141
-ADD AX,#0x1111
+ADD AX,#0xDEAD
+ADD CX,#0xBEEF
+ADD CX,#0x4111
+ADD AX,#0x2200

cpu/processor.v

@@ -89,6 +89,9 @@ reg [15:0] temp_out;
 ADDER16 ADDER16_1(ADDER16_1A,ADDER16_1B,ALU_OUT,ADDER16_1O,ADDER16_1C);
 
 /*** Processor stages ***/
+
+`define invalid_instruction state=`PROC_IF_STATE_ENTRY;EXCEPTION=1;
+
 always @(negedge clock) begin
 	case(state)
 		`PROC_IF_WRITE_CIR:begin
@@ -107,13 +110,14 @@ always @(negedge clock) begin
 		end
 		`PROC_EX_STATE_EXIT:begin
 			case(out_sel)
-				2'b01:begin
+				2'b11:begin
 					reg_write=0;
+					state=`PROC_IF_STATE_ENTRY;
 				end
 				default:begin
+					`invalid_instruction
 				end
 			endcase
-			state=`PROC_IF_STATE_ENTRY;
 		end
 		`PROC_DE_LOAD_16_EXTRA_FETCH_SET:begin
 			external_address_bus = ProgCount;
@@ -122,8 +126,6 @@ always @(negedge clock) begin
 	endcase
 end
 
-`define invalid_instruction state=`PROC_IF_STATE_ENTRY;EXCEPTION=1;
-
 always @(posedge clock) begin
 	case(state)
 		`PROC_HALT_STATE:
@@ -151,7 +153,7 @@ always @(posedge clock) begin
 						unaligned_access=~unaligned_access;
 						in1_sel=2'b00;
 						in2_sel=2'b01;
-						out_sel=2'b01;
+						out_sel=2'b11;
 						reg_read_addr=3'b000;
 						reg_addr=3'b000;
 						reg_read_read=0;
@@ -172,7 +174,7 @@ always @(posedge clock) begin
 							end
 							in1_sel=2'b00;
 							in2_sel=2'b01;
-							out_sel=2'b01;
+							out_sel=CIR[7:6];
 							reg_read_addr=CIR[2:0];
 							reg_addr=CIR[2:0];
 							reg_read_read=0;
@@ -196,7 +198,7 @@ always @(posedge clock) begin
 								end
 								in1_sel=2'b00;
 								in2_sel=2'b01;
-								out_sel=2'b01;
+								out_sel=CIR[7:6];
 								PARAM1=1;
 								reg_read_addr=CIR[2:0];
 								reg_addr=CIR[2:0];
@@ -219,17 +221,18 @@ always @(posedge clock) begin
 		end
 		`PROC_DE_LOAD_16_PARAM:begin
 			if(unaligned_access==1)begin
-				PARAM1[15:8] = external_data_bus[7:0];
+				PARAM1[7:0] = external_data_bus[7:0];
 				ProgCount=ProgCount+1;
 				state=`PROC_DE_LOAD_16_EXTRA_FETCH_SET;
 			end else begin
-				PARAM1 <= external_data_bus;
+				PARAM1[7:0] = external_data_bus[15:8];
+				PARAM1[15:8] = external_data_bus[7:0];
 				ProgCount=ProgCount+1;
 				state=`PROC_EX_STATE_ENTRY;
 			end
 		end
 		`PROC_DE_LOAD_16_EXTRA_FETCH:begin
-			PARAM1[7:0] = external_data_bus[15:8];
+			PARAM1[15:8] = external_data_bus[15:8];
 			state=`PROC_EX_STATE_ENTRY;
 		end
 		`PROC_EX_STATE_ENTRY:begin