Fixed a memory corruption bug

system/biu.v

@@ -28,7 +28,6 @@
 `define BIU_PUT_BYTE			4'b0100
 `define BIU_PUT_UNALIGNED_16BIT_DATA	4'b0101
 `define BIU_PUT_ALIGNED_16BIT_DATA	4'b0110
-`define BIU_PUT_UNALIGNED_PREP_NEXT	4'b0111
 `define BIU_PUT_UNALIGNED_PREP_NEXT2	4'b1000
 `define BIU_WRITE_EXIT			4'b1001
 `define BIU_WRITE_RELEASE		4'b1010
@@ -42,7 +41,8 @@ module BIU (
 /*outside world*/ input clock, input reset, output reg [19:0] external_address_bus,
 /*             */ inout [15:0] external_data_bus,output reg read, output reg write,output reg BHE,output reg IOMEM,
 /*  internal   */ output reg [31:0] INSTRUCTION, output reg VALID_INSTRUCTION, output reg [15:0] INSTRUCTION_LOCATION, input [1:0] NEXT_POSITION,
-/*             */ input[15:0] ADDRESS_INPUT, inout [15:0] DATA, input write_request, input read_request, input Wbit, output reg VALID_DATA, input MEM_OR_IO
+/*             */ input[15:0] ADDRESS_INPUT, inout [15:0] DATA, input write_request, input read_request, input Wbit, output reg VALID_DATA, input MEM_OR_IO,
+/*             */ input [`PROC_STATE_BITS-1:0] proc_state, input SIMPLE_MICRO
 	);
 
 reg [15:0] data_bus_output_register;
@@ -177,9 +177,6 @@ always @(posedge clock) begin
 				`endif
 				BHE <= 0;
 				data_bus_output_register <= {DATA[7:0],DATA[15:8]};
-				biu_state <= `BIU_PUT_UNALIGNED_PREP_NEXT;
-			end
-			`BIU_PUT_UNALIGNED_PREP_NEXT:begin
 				write <= 0;
 				biu_state <= `BIU_PUT_UNALIGNED_PREP_NEXT2;
 			end
@@ -194,14 +191,14 @@ always @(posedge clock) begin
 					$display("Writing 16bit %04x at %04x",DATA,DATA_ADDRESS);
 				`endif
 				data_bus_output_register <= {DATA[15:8],DATA[7:0]};
-				biu_state <= `BIU_WRITE_EXIT;
+				write <= 0;
+				biu_state <= `BIU_WRITE_RELEASE;
 			end
 
 			`BIU_PUT_BYTE:begin
 				`ifdef DEBUG_DATA_READ_WRITES
 					$display("Writing 8bit %02x at %04x",DATA[7:0],DATA_ADDRESS);
 				`endif
-				biu_state <= `BIU_WRITE_EXIT;
 				if(ADDRESS_INPUT[0:0]==0) begin
 					BHE <= 1;
 					data_bus_output_register <= {8'b0,DATA[7:0]};
@@ -209,6 +206,8 @@ always @(posedge clock) begin
 					BHE <= 0;
 					data_bus_output_register <= {DATA[7:0],8'b0};
 				end
+				write <= 0;
+				biu_state <= `BIU_WRITE_RELEASE;
 			end
 			`BIU_WRITE_EXIT:begin
 				write <= 0;
@@ -278,6 +277,7 @@ always @(posedge clock) begin
 				VALID_INSTRUCTION <= 0;
 				VALID_DATA <= 0;
 				DATA_DIR <= 0;
+				was_dec <= 0;
 			end
 			default: begin
 				biu_state <= `BIU_NEXT_ACTION;/*Should be unreachable*/
@@ -293,19 +293,47 @@ wire [2:0] fifoIsize;
 wire Isit1;
 /* verilator lint_on UNDRIVEN */
 `ifdef EARLY_VALID_INSTRUCTION
-InstrSize fifoInstrSize({INPUT_FIFO[FIFO_start][7:0],INPUT_FIFO[FIFO_start][5:3]},fifoIsize);
+InstrSize fifoInstrSize({INPUT_FIFO[FIFO_start][7:0],INPUT_FIFO[FIFO_start+1][5:3]},fifoIsize);
 Is1 Is1(INPUT_FIFO[FIFO_start][7:0],Isit1);
 `endif
 
+reg was_dec;
+reg was_simple;
+
+always @( proc_state ) begin
+	case (proc_state)
+		`PROC_DE_STATE_ENTRY: begin
+				was_dec<=1;
+		end
+		default: begin
+			if( SIMPLE_MICRO==0 && was_dec==1 )begin
+					was_dec<=0;
+					/* verilator lint_off BLKSEQ */
+					FIFO_start = FIFO_start + {1'b0,Isize};
+					INSTRUCTION_LOCATION <= INSTRUCTION_LOCATION + {12'b0,Isize};;
+					/* verilator lint_on BLKSEQ */
+					VALID_INSTRUCTION <= 0;
+			end else if ( SIMPLE_MICRO==1 && was_simple == 1) begin
+					was_simple<=0;
+					was_dec<=0;
+					/* verilator lint_off BLKSEQ */
+					FIFO_start = FIFO_start + {1'b0,Isize};
+					INSTRUCTION_LOCATION <= INSTRUCTION_LOCATION + {12'b0,Isize};;
+					/* verilator lint_on BLKSEQ */
+					VALID_INSTRUCTION <= 0;
+			end
+		end
+	endcase
+end
+
+always @( negedge SIMPLE_MICRO ) begin
+	was_simple <= 1;
+end
+
 always @( NEXT_POSITION ) begin
 	case(NEXT_POSITION)
 		2'b00:begin end /* no action */
 		2'b01:begin /* Next instruction */
-			/* verilator lint_off BLKSEQ */
-			FIFO_start = FIFO_start + {1'b0,Isize};
-			INSTRUCTION_LOCATION <= INSTRUCTION_LOCATION + {12'b0,Isize};;
-			/* verilator lint_on BLKSEQ */
-			VALID_INSTRUCTION <= 0;
 		end
 		2'b10:begin /* Jump to specific location based on register */
 			jump_req <= 1;

system/decoder.v

@@ -92,7 +92,7 @@ microcode ucode(seq_addr_input,ucode_data);
 // then branching off of that instead of the raw bits. otherwise the code
 // would be identical
 // verilator lint_off BLKSEQ
-always @( CIR or SIMPLE_MICRO or seq_addr_input ) begin
+always @( FLAGS or CIR or SIMPLE_MICRO or seq_addr_input ) begin
 	if (SIMPLE_MICRO==0)begin
 		casez({CIR[15:8],CIR[5:3]})
 			11'b0000_010?_??? : begin

system/memory.v

@@ -38,10 +38,12 @@ assign data[7:0] = !address[0:0] & !rd & !cs ? memory[address[16:1]][15:8]  : 8'
 assign data[15:8] =     !BHE     & !rd & !cs ? memory[address[16:1]][7:0]   : 8'hz;
 
 always @(negedge wr) begin
-	if(BHE==0)
-		memory[address[16:1]][7:0]<=data[15:8];
-	if(address[0]==0)
-		memory[address[16:1]][15:8]<=data[7:0];
+	if( cs == 0 ) begin
+		if(BHE==0)
+			memory[address[16:1]][7:0]<=data[15:8];
+		if(address[0]==0)
+			memory[address[16:1]][15:8]<=data[7:0];
+	end
 end
 
 endmodule

system/processor.v

@@ -49,7 +49,8 @@ wire BIU_VALID_DATA;
 
 BIU BIU(
 	clock,reset,external_address_bus,external_data_bus,read,write,BHE,IOMEM,
-	INSTRUCTION,VALID_INSTRUCTION,INSTRUCTION_LOCATION,BIU_NEXT_POSITION,BIU_ADDRESS_INPUT,BIU_DATA,biu_write_request,biu_read_request,Wbit,BIU_VALID_DATA,MEM_OR_IO
+	INSTRUCTION,VALID_INSTRUCTION,INSTRUCTION_LOCATION,BIU_NEXT_POSITION,BIU_ADDRESS_INPUT,BIU_DATA,biu_write_request,biu_read_request,Wbit,BIU_VALID_DATA,MEM_OR_IO,
+	state,SIMPLE_MICRO
 );
 assign BIU_DATA= biu_data_direction ? 16'hz : (memio_address_select?reg_read_port1_data:ALU_1O);
 
@@ -411,7 +412,7 @@ always @(posedge clock) begin
 			end
 		end
 		`PROC_NEXT_INSTRUCTION:begin
-			BIU_NEXT_POSITION <= 2'b01;
+			/*necessary for biu to see we went on another state from decode to give us a new instruction*/
 			state <= `PROC_DE_STATE_ENTRY;
 		end
 		`PROC_EX_STATE_ENTRY:begin
@@ -460,8 +461,6 @@ always @(posedge clock) begin
 								state <= `PROC_MEMIO_WRITE;
 							end
 						endcase
-						if(BIU_NEXT_POSITION != 2'b10 )
-							BIU_NEXT_POSITION <= 2'b01;
 				end
 				3'b011:begin
 					reg_write_we <= 0;
@@ -469,16 +468,12 @@ always @(posedge clock) begin
 						state <= `PROC_DE_STATE_ENTRY;
 					else
 						state <= `PROC_NEXT_MICROCODE;
-					if(BIU_NEXT_POSITION != 2'b10 )
-						BIU_NEXT_POSITION <= 2'b01;
 				end
 				3'b100:begin /*No output*/
 					if (ucode_seq_addr==`UCODE_NO_INSTRUCTION)
 						state <= `PROC_DE_STATE_ENTRY;
 					else
 						state <= `PROC_NEXT_MICROCODE;
-					if(BIU_NEXT_POSITION != 2'b10 )
-						BIU_NEXT_POSITION <= 2'b01;
 				end
 				3'b101:begin /* Program Counter*/
 					BIU_ADDRESS_INPUT <= ALU_1O[15:0];
@@ -492,8 +487,6 @@ always @(posedge clock) begin
 				3'b110:begin /* SP Indirect write*/
 					reg_read_port1_addr <= 4'b1100;
 					state <= `PROC_MEMIO_WRITE;
-					if(BIU_NEXT_POSITION != 2'b10 )
-						BIU_NEXT_POSITION <= 2'b01;
 				end
 				3'b111:begin /* Write to PRAM1 (for microcode calculations) */
 					PARAM1 <= ALU_1O;
@@ -501,8 +494,6 @@ always @(posedge clock) begin
 						state <= `PROC_DE_STATE_ENTRY;
 					else
 						state <= `PROC_NEXT_MICROCODE;
-					if(BIU_NEXT_POSITION != 2'b10 )
-						BIU_NEXT_POSITION <= 2'b01;
 				end
 				default:begin
 					`unimpl_addressing_mode