From eb7cc9dc79004211b45c55d94d0a8eb4f23330d7 Mon Sep 17 00:00:00 2001
From: Austin Morlan <mail@austinmorlan.com>
Date: Thu, 16 Feb 2023 19:25:05 -0800
Subject: [PATCH] Add rst and remove en from SAP-1 and SAP-2

---
 src/sap1/adder.v      |   9 +--
 src/sap1/clock.v      |   3 +-
 src/sap1/controller.v |  91 ++++++++++--------------
 src/sap1/ir.v         |  17 +++--
 src/sap1/memory.v     |  15 ++--
 src/sap1/pc.v         |  13 ++--
 src/sap1/reg_a.v      |  18 ++---
 src/sap1/reg_b.v      |  14 ++--
 src/sap1/top.v        | 116 ++++++++++++++++++------------
 src/sap1/top_tb.v     | 115 ++++++++++++++++++------------
 src/sap2/alu.v        |  17 +++--
 src/sap2/controller.v |  35 +++++----
 src/sap2/flags.v      |  23 +++---
 src/sap2/ir.v         |  14 ++--
 src/sap2/memory.v     |  46 ++++++------
 src/sap2/pc.v         |  14 ++--
 src/sap2/register.v   |  13 ++--
 src/sap2/top.v        | 162 +++++++++++++++++-------------------------
 src/sap2/top_tb.v     | 162 +++++++++++++++++-------------------------
 19 files changed, 448 insertions(+), 449 deletions(-)

diff --git a/src/sap1/adder.v b/src/sap1/adder.v
index 1a0a495..747ed7b 100644
--- a/src/sap1/adder.v
+++ b/src/sap1/adder.v
@@ -2,13 +2,10 @@ module adder(
 	input[7:0] a,
 	input[7:0] b,
 	input sub,
-	input en,
-	output[7:0] bus);
+	output[7:0] out
+);
 
-assign bus = 
-	(en) ? 
-		((sub) ? a-b : a+b) :
-		8'bz;
+assign out = (sub) ? a-b : a+b;
 
 endmodule
 
diff --git a/src/sap1/clock.v b/src/sap1/clock.v
index 451d6fb..cef4bfc 100644
--- a/src/sap1/clock.v
+++ b/src/sap1/clock.v
@@ -1,7 +1,8 @@
 module clock(
 	input hlt,
 	input clk_in,
-	output clk_out);
+	output clk_out
+);
 
 assign clk_out = (hlt) ? 1'b0 : clk_in;
 
diff --git a/src/sap1/controller.v b/src/sap1/controller.v
index 02c94f5..21fefd4 100644
--- a/src/sap1/controller.v
+++ b/src/sap1/controller.v
@@ -1,7 +1,9 @@
 module controller(
 	input clk,
-	input[3:0] instr,
-	output reg[11:0] ctrl_word);
+	input rst,
+	input[3:0] opcode,
+	output[11:0] out
+);
 
 localparam SIG_HLT       = 11;
 localparam SIG_PC_INC    = 10;
@@ -21,103 +23,88 @@ localparam OP_ADD = 4'b0001;
 localparam OP_SUB = 4'b0010;
 localparam OP_HLT = 4'b1111;
 
-reg[2:0] stage = 0;
+reg[2:0]  stage;
+reg[11:0] ctrl_word;
 
-always @(negedge clk) begin
-	if (stage == 6) begin
-		stage <= 1;
+always @(negedge clk, posedge rst) begin
+	if (rst) begin
+		stage <= 0;
 	end else begin
-		stage <= stage + 1;
+		if (stage == 5) begin
+			stage <= 0;
+		end else begin
+			stage <= stage + 1;
+		end
 	end
 end
 
 always @(*) begin
+	ctrl_word = 12'b0;
+
 	case (stage)
-		1: begin
-			ctrl_word = 12'b0;
+		0: begin
 			ctrl_word[SIG_PC_EN] = 1;
 			ctrl_word[SIG_MEM_LOAD] = 1;
 		end
-		2: begin
-			ctrl_word = 12'b0;
+		1: begin
 			ctrl_word[SIG_PC_INC] = 1;
 		end
-		3: begin
-			ctrl_word = 12'b0;
+		2: begin
 			ctrl_word[SIG_MEM_EN] = 1;
 			ctrl_word[SIG_IR_LOAD] = 1;
 		end
-		4: begin
-			case (instr)
+		3: begin
+			case (opcode)
 				OP_LDA: begin
-					ctrl_word = 12'b0;
 					ctrl_word[SIG_IR_EN] = 1;
 					ctrl_word[SIG_MEM_LOAD] = 1;
 				end
 				OP_ADD: begin
-					ctrl_word = 12'b0;
 					ctrl_word[SIG_IR_EN] = 1;
 					ctrl_word[SIG_MEM_LOAD] = 1;
 				end
 				OP_SUB: begin
-					ctrl_word = 12'b0;
 					ctrl_word[SIG_IR_EN] = 1;
 					ctrl_word[SIG_MEM_LOAD] = 1;
 				end
 				OP_HLT: begin
-					ctrl_word = 12'b0;
 					ctrl_word[SIG_HLT] = 1;
 				end
-				default: begin
-					ctrl_word = 12'b0;
+			endcase
+		end
+		4: begin
+			case (opcode)
+				OP_LDA: begin
+					ctrl_word[SIG_MEM_EN] = 1;
+					ctrl_word[SIG_A_LOAD] = 1;
+				end
+				OP_ADD: begin
+					ctrl_word[SIG_MEM_EN] = 1;
+					ctrl_word[SIG_B_LOAD] = 1;
+				end
+				OP_SUB: begin
+					ctrl_word[SIG_MEM_EN] = 1;
+					ctrl_word[SIG_B_LOAD] = 1;
 				end
 			endcase
 		end
 		5: begin
-			case (instr)
-				OP_LDA: begin
-					ctrl_word = 12'b0;
-					ctrl_word[SIG_MEM_EN] = 1;
-					ctrl_word[SIG_A_LOAD] = 1;
-				end
+			case (opcode)
 				OP_ADD: begin
-					ctrl_word = 12'b0;
-					ctrl_word[SIG_MEM_EN] = 1;
-					ctrl_word[SIG_B_LOAD] = 1;
-				end
-				OP_SUB: begin
-					ctrl_word = 12'b0;
-					ctrl_word[SIG_MEM_EN] = 1;
-					ctrl_word[SIG_B_LOAD] = 1;
-				end
-				default: begin
-					ctrl_word = 12'b0;
-				end
-			endcase
-		end
-		6: begin
-			case (instr)
-				OP_ADD: begin
-					ctrl_word = 12'b0;
 					ctrl_word[SIG_ADDER_EN] = 1;
 					ctrl_word[SIG_A_LOAD] = 1;
 				end
 				OP_SUB: begin
-					ctrl_word = 12'b0;
 					ctrl_word[SIG_ADDER_SUB] = 1;
 					ctrl_word[SIG_ADDER_EN] = 1;
 					ctrl_word[SIG_A_LOAD] = 1;
 				end
-				default: begin
-					ctrl_word = 12'b0;
-				end
 			endcase
 		end
-		default: begin
-			ctrl_word = 12'b0;
-		end
 	endcase
 end
 
+assign out = ctrl_word;
+
 endmodule
 
diff --git a/src/sap1/ir.v b/src/sap1/ir.v
index 9694b06..da0cd84 100644
--- a/src/sap1/ir.v
+++ b/src/sap1/ir.v
@@ -1,23 +1,22 @@
 module ir(
 	input clk,
-	input clr,
+	input rst,
 	input load,
-	input en,
-	inout[7:0] bus,
-	output[3:0] instr);
+	input[7:0] bus,
+	output[7:0] out
+);
 
-reg[7:0] ir = 0;
+reg[7:0] ir;
 
-always @(posedge clk or posedge clr) begin
-	if (clr) begin
+always @(posedge clk, posedge rst) begin
+	if (rst) begin
 		ir <= 8'b0;
 	end else if (load) begin
 		ir <= bus;
 	end
 end
 
-assign instr = ir[7:4];
-assign bus = (en) ? ir[3:0] : 8'bz;
+assign out = ir;
 
 endmodule
 
diff --git a/src/sap1/memory.v b/src/sap1/memory.v
index 1b9f3ed..0b1b990 100644
--- a/src/sap1/memory.v
+++ b/src/sap1/memory.v
@@ -1,24 +1,27 @@
 module memory(
 	input clk,
+	input rst,
 	input load,
-	input en,
-	inout[7:0] bus
+	input[7:0] bus,
+	output[7:0] out
 );
 
 initial begin
 	$readmemh("program.bin", ram);
 end
 
-reg[3:0] mar = 0;
+reg[3:0] mar;
 reg[7:0] ram[0:15];
 
-always @(posedge clk) begin
-	if (load) begin
+always @(posedge clk, posedge rst) begin
+	if (rst) begin
+		mar <= 4'b0;
+	end else if (load) begin
 		mar <= bus[3:0];
 	end
 end
 
-assign bus = (en) ? ram[mar] : 8'bz;
+assign out = ram[mar];
 
 endmodule
 
diff --git a/src/sap1/pc.v b/src/sap1/pc.v
index 5c216e6..8c767ba 100644
--- a/src/sap1/pc.v
+++ b/src/sap1/pc.v
@@ -1,22 +1,21 @@
 module pc(
 	input clk,
-	input clr,
+	input rst,
 	input inc,
-	input en,
-	output[7:0] bus
+	output[7:0] out
 );
 
-reg[3:0] pc = 0;
+reg[3:0] pc;
 
-always @(posedge clk or posedge clr) begin
-	if (clr) begin
+always @(posedge clk, posedge rst) begin
+	if (rst) begin
 		pc <= 4'b0;
 	end else if (inc) begin
 		pc <= pc + 1;
 	end
 end
 
-assign bus = (en) ? pc : 8'bz;
+assign out = pc;
 
 endmodule
 
diff --git a/src/sap1/reg_a.v b/src/sap1/reg_a.v
index 89f2f0b..5deba00 100644
--- a/src/sap1/reg_a.v
+++ b/src/sap1/reg_a.v
@@ -1,20 +1,22 @@
 module reg_a(
 	input clk,
+	input rst,
 	input load,
-	input en,
-	inout[7:0] bus,
-	output[7:0] val);
+	input[7:0] bus,
+	output[7:0] out
+);
 
-reg[7:0] reg_a = 0;
+reg[7:0] reg_a;
 
-always @(posedge clk) begin
-	if (load) begin
+always @(posedge clk, posedge rst) begin
+	if (rst) begin
+		reg_a <= 8'b0;
+	end else if (load) begin
 		reg_a <= bus;
 	end
 end
 
-assign bus = (en) ? reg_a : 8'bz;
-assign val = reg_a;
+assign out = reg_a;
 
 endmodule
 
diff --git a/src/sap1/reg_b.v b/src/sap1/reg_b.v
index 30c57a6..8190261 100644
--- a/src/sap1/reg_b.v
+++ b/src/sap1/reg_b.v
@@ -1,18 +1,22 @@
 module reg_b(
 	input clk,
+	input rst,
 	input load,
 	input[7:0] bus,
-	output[7:0] val);
+	output[7:0] out
+);
 
-reg[7:0] reg_b = 0;
+reg[7:0] reg_b;
 
-always @(posedge clk) begin
-	if (load) begin
+always @(posedge clk, posedge rst) begin
+	if (rst) begin
+		reg_b <= 8'b0;
+	end else if (load) begin
 		reg_b <= bus;
 	end
 end
 
-assign val = reg_b;
+assign out = reg_b;
 
 endmodule
 
diff --git a/src/sap1/top.v b/src/sap1/top.v
index 46eab98..b525e16 100644
--- a/src/sap1/top.v
+++ b/src/sap1/top.v
@@ -1,82 +1,108 @@
 module top(
-	input CLK);
+	input CLK
+);
 
-wire[7:0] bus;
 
-wire clk;
+reg[7:0] bus;
+
+always @(*) begin
+	if (ir_en) begin
+		bus = ir_out;
+	end else if (adder_en) begin
+		bus = adder_out;
+	end else if (a_en) begin
+		bus = a_out;
+	end else if (mem_en) begin
+		bus = mem_out;
+	end else if (pc_en) begin
+		bus = pc_out;
+	end else begin
+		bus = 8'b0;
+	end
+end
+
+wire rst;
 wire hlt;
+wire clk;
 clock clock(
 	.hlt(hlt),
 	.clk_in(CLK),
 	.clk_out(clk)
 );
 
-wire clr;
-wire pc_en;
 wire pc_inc;
+wire pc_en;
+wire[7:0] pc_out;
 pc pc(
 	.clk(clk),
-	.clr(clr),
+	.rst(rst),
 	.inc(pc_inc),
-	.en(pc_en),
-	.bus(bus)
+	.out(pc_out)
 );
 
-wire a_load;
-wire a_en;
-wire[7:0] a_val;
-reg_a reg_a(
-	.clk(clk),
-	.load(a_load),
-	.en(a_en),
-	.bus(bus),
-	.val(a_val)
-);
-
-wire b_load;
-wire[7:0] b_val;
-reg_b reg_b(
-	.clk(clk),
-	.load(b_load),
-	.bus(bus),
-	.val(b_val)
-);
-
-wire adder_sub;
-wire adder_en;
-adder adder(
-	.a(a_val),
-	.b(b_val),
-	.sub(adder_sub),
-	.en(adder_en),
-	.bus(bus)
-);
 
 wire mar_load;
 wire mem_en;
+wire[7:0] mem_out;
 memory mem(
 	.clk(clk),
+	.rst(rst),
 	.load(mar_load),
-	.en(mem_en),
-	.bus(bus)
+	.bus(bus),
+	.out(mem_out)
 );
 
+
+wire a_load;
+wire a_en;
+wire[7:0] a_out;
+reg_a reg_a(
+	.clk(clk),
+	.rst(rst),
+	.load(a_load),
+	.bus(bus),
+	.out(a_out)
+);
+
+
+wire b_load;
+wire[7:0] b_out;
+reg_b reg_b(
+	.clk(clk),
+	.rst(rst),
+	.load(b_load),
+	.bus(bus),
+	.out(b_out)
+);
+
+
+wire adder_sub;
+wire adder_en;
+wire[7:0] adder_out;
+adder adder(
+	.a(a_out),
+	.b(b_out),
+	.sub(adder_sub),
+	.out(adder_out)
+);
+
+
 wire ir_load;
 wire ir_en;
-wire[3:0] ir_instr;
+wire[7:0] ir_out;
 ir ir(
 	.clk(clk),
-	.clr(clr),
+	.rst(rst),
 	.load(ir_load),
-	.en(ir_en),
 	.bus(bus),
-	.instr(ir_instr)
+	.out(ir_out)
 );
 
 controller controller(
 	.clk(clk),
-	.instr(ir_instr),
-	.ctrl_word(
+	.rst(rst),
+	.opcode(ir_out[7:4]),
+	.out(
 	{
 		hlt,
 		pc_inc,
diff --git a/src/sap1/top_tb.v b/src/sap1/top_tb.v
index ce87d1b..35266cd 100644
--- a/src/sap1/top_tb.v
+++ b/src/sap1/top_tb.v
@@ -1,8 +1,29 @@
 module top_tb();
 
+
 initial begin
 	$dumpfile("top_tb.vcd");
 	$dumpvars(0, top_tb);
+	rst = 1;
+	#1 rst = 0;
+end
+
+reg[7:0] bus;
+
+always @(*) begin
+	if (ir_en) begin
+		bus = ir_out;
+	end else if (adder_en) begin
+		bus = adder_out;
+	end else if (a_en) begin
+		bus = a_out;
+	end else if (mem_en) begin
+		bus = mem_out;
+	end else if (pc_en) begin
+		bus = pc_out;
+	end else begin
+		bus = 8'b0;
+	end
 end
 
 reg clk_in = 0;
@@ -15,80 +36,86 @@ end
 
 wire clk;
 wire hlt;
-wire clr;
-wire[7:0] bus;
-
+reg rst;
 clock clock(
 	.hlt(hlt),
 	.clk_in(clk_in),
 	.clk_out(clk)
 );
 
-wire pc_en;
 wire pc_inc;
+wire[7:0] pc_out;
+wire pc_en;
 pc pc(
 	.clk(clk),
-	.clr(clr),
+	.rst(rst),
 	.inc(pc_inc),
-	.en(pc_en),
-	.bus(bus)
+	.out(pc_out)
 );
 
-wire a_load;
-wire a_en;
-wire[7:0] a_val;
-reg_a reg_a(
-	.clk(clk),
-	.load(a_load),
-	.en(a_en),
-	.bus(bus),
-	.val(a_val)
-);
-
-wire b_load;
-wire[7:0] b_val;
-reg_b reg_b(
-	.clk(clk),
-	.load(b_load),
-	.bus(bus),
-	.val(b_val)
-);
-
-wire adder_sub;
-wire adder_en;
-adder adder(
-	.a(a_val),
-	.b(b_val),
-	.sub(adder_sub),
-	.en(adder_en),
-	.bus(bus)
-);
 
 wire mar_load;
 wire mem_en;
+wire[7:0] mem_out;
 memory mem(
 	.clk(clk),
+	.rst(rst),
 	.load(mar_load),
-	.en(mem_en),
-	.bus(bus)
+	.bus(bus),
+	.out(mem_out)
 );
 
+
+wire a_load;
+wire a_en;
+wire[7:0] a_out;
+reg_a reg_a(
+	.clk(clk),
+	.rst(rst),
+	.load(a_load),
+	.bus(bus),
+	.out(a_out)
+);
+
+
+wire b_load;
+wire[7:0] b_out;
+reg_b reg_b(
+	.clk(clk),
+	.rst(rst),
+	.load(b_load),
+	.bus(bus),
+	.out(b_out)
+);
+
+
+wire adder_sub;
+wire adder_en;
+wire[7:0] adder_out;
+adder adder(
+	.a(a_out),
+	.b(b_out),
+	.sub(adder_sub),
+	.out(adder_out)
+);
+
+
 wire ir_load;
 wire ir_en;
-wire[3:0] ir_instr;
+wire[7:0] ir_out;
 ir ir(
 	.clk(clk),
-	.clr(clr),
+	.rst(rst),
 	.load(ir_load),
-	.en(ir_en),
 	.bus(bus),
-	.instr(ir_instr)
+	.out(ir_out)
 );
 
 controller controller(
 	.clk(clk),
-	.instr(ir_instr),
-	.ctrl_word(
+	.rst(rst),
+	.opcode(ir_out[7:4]),
+	.out(
 	{
 		hlt,
 		pc_inc,
diff --git a/src/sap2/alu.v b/src/sap2/alu.v
index b0a4c40..1dae769 100644
--- a/src/sap2/alu.v
+++ b/src/sap2/alu.v
@@ -1,14 +1,15 @@
 module alu(
 	input clk,
+	input rst,
 	input[7:0] a,
 	input[2:0] op,
 	input load,
-	input en,
-	inout[15:0] bus
+	input[15:0] bus,
+	output[7:0] out
 );
 
-reg[7:0] alu = 0;
-reg[7:0] tmp = 0;
+reg[7:0] alu;
+reg[7:0] tmp;
 
 localparam OP_ADD = 0;
 localparam OP_SUB = 1;
@@ -19,8 +20,10 @@ localparam OP_CMA = 5;
 localparam OP_RAL = 6;
 localparam OP_RAR = 7;
 
-always @(posedge clk) begin
-	if (load) begin
+always @(posedge clk, posedge rst) begin
+	if (rst) begin
+		tmp <= 8'b0;
+	end else if (load) begin
 		tmp <= bus[7:0];
 	end
 end
@@ -58,7 +61,7 @@ always @(*) begin
 	endcase
 end
 
-assign bus = (en) ? alu : 16'bz;
+assign out = alu;
 
 endmodule
 
diff --git a/src/sap2/controller.v b/src/sap2/controller.v
index 4718647..eeb96ba 100644
--- a/src/sap2/controller.v
+++ b/src/sap2/controller.v
@@ -1,8 +1,9 @@
 module controller(
 	input clk,
-	input[7:0] instr,
+	input rst,
+	input[7:0] opcode,
 	input[1:0] flags,
-	output reg[33:0] ctrl_word
+	output[33:0] out
 );
 
 localparam SIG_END       = 34;
@@ -48,33 +49,41 @@ localparam OP_JM  = 8'hFA;
 localparam FLAG_Z = 1;
 localparam FLAG_S = 0;
 
+reg[34:0] ctrl_word;
+
 reg[34:0] ctrl_rom[0:4095];
 initial begin
 	$readmemb("ctrl_rom.bin", ctrl_rom);
 end
 
-reg      reset = 0;
-reg[3:0] stage = 0;
-always @(negedge clk) begin
-	if (reset) begin
+reg[3:0] stage;
+always @(negedge clk, posedge rst) begin
+	if (rst) begin
 		stage <= 0;
 	end else begin
-		stage <= stage + 1;
+		if (stage_rst) begin
+			stage <= 0;
+		end else begin
+			stage <= stage + 1;
+		end
 	end
 end
 
+reg stage_rst;
 always @(*) begin
-	ctrl_word = ctrl_rom[{instr, stage}];
+	ctrl_word = ctrl_rom[{opcode, stage}];
 
-	if ((instr == OP_JZ  && stage == 4 && flags[FLAG_Z] == 0) ||
-		(instr == OP_JNZ && stage == 4 && flags[FLAG_Z] == 1) ||
-		(instr == OP_JM  && stage == 4 && flags[FLAG_S] == 0))
+	if ((opcode == OP_JZ  && stage == 4 && flags[FLAG_Z] == 0) ||
+		(opcode == OP_JNZ && stage == 4 && flags[FLAG_Z] == 1) ||
+		(opcode == OP_JM  && stage == 4 && flags[FLAG_S] == 0))
 	begin
-		reset = 1;
+		stage_rst = 1;
 	end else begin
-		reset = ctrl_rom[{instr, stage}][SIG_END];
+		stage_rst = ctrl_rom[{opcode, stage}][SIG_END];
 	end
 end
 
+assign out = ctrl_word;
+
 endmodule
 
diff --git a/src/sap2/flags.v b/src/sap2/flags.v
index 9ace739..2e047c3 100644
--- a/src/sap2/flags.v
+++ b/src/sap2/flags.v
@@ -1,5 +1,6 @@
 module flags(
 	input clk,
+	input rst,
 	input[7:0] a,
 	input[7:0] b,
 	input[7:0] c,
@@ -12,22 +13,24 @@ module flags(
 localparam FLAG_Z = 1;
 localparam FLAG_S = 0;
 
-reg[1:0] data = 0;
+reg[1:0] flags;
 
-always @(negedge clk) begin
-	if (load_a) begin
-		data[FLAG_Z] <= (a == 0) ? 1'b1 : 1'b0;
-		data[FLAG_S] <= (a[7] == 1) ? 1'b1 : 1'b0;
+always @(negedge clk, posedge rst) begin
+	if (rst) begin
+		flags <= 2'b0;
+	end else if (load_a) begin
+		flags[FLAG_Z] <= (a == 0) ? 1'b1 : 1'b0;
+		flags[FLAG_S] <= (a[7] == 1) ? 1'b1 : 1'b0;
 	end else if (load_b) begin
-		data[FLAG_Z] <= (b == 0) ? 1'b1 : 1'b0;
-		data[FLAG_S] <= (b[7] == 1) ? 1'b1 : 1'b0;
+		flags[FLAG_Z] <= (b == 0) ? 1'b1 : 1'b0;
+		flags[FLAG_S] <= (b[7] == 1) ? 1'b1 : 1'b0;
 	end else if (load_c) begin
-		data[FLAG_Z] <= (c == 0) ? 1'b1 : 1'b0;
-		data[FLAG_S] <= (c[7] == 1) ? 1'b1 : 1'b0;
+		flags[FLAG_Z] <= (c == 0) ? 1'b1 : 1'b0;
+		flags[FLAG_S] <= (c[7] == 1) ? 1'b1 : 1'b0;
 	end
 end
 
-assign out = data;
+assign out = flags;
 
 endmodule
 
diff --git a/src/sap2/ir.v b/src/sap2/ir.v
index 095ac24..ed7f0a3 100644
--- a/src/sap2/ir.v
+++ b/src/sap2/ir.v
@@ -1,22 +1,22 @@
 module ir(
 	input clk,
-	input clr,
+	input rst,
 	input load,
 	input[15:0] bus,
 	output[7:0] out
 );
 
-reg[7:0] data = 0;
+reg[7:0] ir;
 
-always @(posedge clk or posedge clr) begin
-	if (clr) begin
-		data <= 8'b0;
+always @(posedge clk, posedge rst) begin
+	if (rst) begin
+		ir <= 8'b0;
 	end else if (load) begin
-		data <= bus[7:0];
+		ir <= bus[7:0];
 	end
 end
 
-assign out = data;
+assign out = ir;
 
 endmodule
 
diff --git a/src/sap2/memory.v b/src/sap2/memory.v
index 800e12c..6236f5d 100644
--- a/src/sap2/memory.v
+++ b/src/sap2/memory.v
@@ -1,30 +1,36 @@
 module memory(
 	input clk,
+	input rst,
 	input mar_loadh,
 	input mar_loadl,
 	input mdr_load,
-	input mdr_en,
 	input ram_load,
 	input ram_enh,
 	input ram_enl,
 	input call,
 	input ret,
-	inout[15:0] bus
+	input[15:0] bus,
+	output[15:0] out
 );
 
 initial begin
 	$readmemh("program.bin", ram);
 end
 
-reg[15:0] mar = 0;
-reg[15:0] mdr = 0;
+reg[15:0] mar;
+reg[15:0] mdr;
 reg[7:0]  ram[0:65535];
 
+always @(posedge rst) begin
+	mar <= 16'b0;
+	mdr <= 16'b0;
+end
+
 always @(posedge clk) begin
 	if (mar_loadh) begin
 		mar[15:8] <= bus[15:8];
 	end
-	
+
 	if (mar_loadl) begin
 		mar[7:0] <= bus[7:0];
 	end
@@ -32,31 +38,23 @@ always @(posedge clk) begin
 	if (mdr_load) begin
 		mdr[7:0] <= bus[7:0];
 	end
-	
-	if (ram_load) begin
-		ram[mar] <= mdr;
-	end 
-
-	if (ram_enh) begin
-		mdr[15:8] <= ram[mar];
-	end
-
-	if (ram_enl) begin
-		mdr[7:0] <= ram[mar];
-	end
-
-	if (call) begin
-		ram[16'hFFFE] <= bus[15:8];
-		ram[16'hFFFF] <= bus[7:0];
-	end
 
 	if (ret) begin
 		mdr[15:8] <= ram[16'hFFFE];
-		mdr[7:0]  <= ram[16'hFFFF];
+		mdr[7:0] <= ram[16'hFFFF];
+	end else if (call) begin
+		ram[16'hFFFE] <= bus[15:8];
+		ram[16'hFFFF] <= bus[7:0];
+	end else if (ram_enh) begin
+		mdr[15:8] <= ram[mar];
+	end else if (ram_enl) begin
+		mdr[7:0] <= ram[mar];
+	end else if (ram_load) begin
+		ram[mar] <= mdr;
 	end
 end
 
-assign bus = (mdr_en) ? mdr : 16'bz;
+assign out = mdr;
 
 endmodule
 
diff --git a/src/sap2/pc.v b/src/sap2/pc.v
index 781f9c0..653f6f1 100644
--- a/src/sap2/pc.v
+++ b/src/sap2/pc.v
@@ -1,16 +1,16 @@
 module pc(
 	input clk,
-	input clr,
+	input rst,
 	input inc,
 	input load,
-	input en,
-	output[15:0] bus
+	input[15:0] bus,
+	output[15:0] out
 );
 
-reg[15:0] pc = 0;
+reg[15:0] pc;
 
-always @(posedge clk or posedge clr) begin
-	if (clr) begin
+always @(posedge clk, posedge rst) begin
+	if (rst) begin
 		pc <= 16'b0;
 	end else if (load) begin
 		pc <= bus;
@@ -19,7 +19,7 @@ always @(posedge clk or posedge clr) begin
 	end
 end
 
-assign bus = (en) ? pc : 16'bz;
+assign out = pc;
 
 endmodule
 
diff --git a/src/sap2/register.v b/src/sap2/register.v
index 83c8c01..35f91b2 100644
--- a/src/sap2/register.v
+++ b/src/sap2/register.v
@@ -1,17 +1,19 @@
 module register(
 	input clk,
+	input rst,
 	input load,
-	input en,
 	input inc,
 	input dec,
-	inout[15:0] bus,
+	input[15:0] bus,
 	output[7:0] out
 );
 
-reg[7:0] data = 0;
+reg[7:0] data;
 
-always @(posedge clk) begin
-	if (load) begin
+always @(posedge clk, posedge rst) begin
+	if (rst) begin
+		data <= 8'b0;
+	end else if (load) begin
 		data <= bus[7:0];
 	end else if (inc) begin
 		data <= data + 1;
@@ -20,7 +22,6 @@ always @(posedge clk) begin
 	end
 end
 
-assign bus = (en) ? {8'b0, data} : 16'bz;
 assign out = data;
 
 endmodule
diff --git a/src/sap2/top.v b/src/sap2/top.v
index f4e2fc4..bf08c4f 100644
--- a/src/sap2/top.v
+++ b/src/sap2/top.v
@@ -3,49 +3,57 @@ module top(
 );
 
 
-wire[15:0] bus;
-wire clr;
+reg[15:0] bus;
+
+always @(*) begin
+	if (a_en) begin
+		bus = a_out;
+	end else if (b_en) begin
+		bus = b_out;
+	end else if (c_en) begin
+		bus = c_out;
+	end else if (alu_en) begin
+		bus = alu_out;
+	end else if (pc_en) begin
+		bus = pc_out;
+	end else if (mdr_en) begin
+		bus = mem_out;
+	end else begin
+		bus = 16'b0;
+	end
+end
+
+
+wire rst;
 wire hlt;
-
-
 wire clk;
 clock clock(
-	// In
 	.hlt(hlt),
 	.clk_in(CLK),
-
-	// Out
 	.clk_out(clk)
 );
 
 wire pc_inc;
 wire pc_load;
 wire pc_en;
+wire[15:0] pc_out;
 pc pc(
-	// In
 	.clk(clk),
-	.clr(clr),
+	.rst(rst),
 	.inc(pc_inc),
 	.load(pc_load),
-	.en(pc_en),
-
-	// Output
-	.bus(bus)
+	.bus(bus),
+	.out(pc_out)
 );
 
 wire ir_load;
-wire[7:0] ir_instr;
+wire[7:0] ir_out;
 ir ir(
-	// In
 	.clk(clk),
-	.clr(clr),
+	.rst(rst),
 	.load(ir_load),
-
-	// Inout
 	.bus(bus),
-
-	// Out
-	.out(ir_instr)
+	.out(ir_out)
 );
 
 wire mar_loadh;
@@ -57,153 +65,115 @@ wire ram_enh;
 wire ram_enl;
 wire call;
 wire ret;
+wire[15:0] mem_out;
 memory mem(
-	// In
 	.clk(clk),
+	.rst(rst),
 	.mar_loadh(mar_loadh),
 	.mar_loadl(mar_loadl),
 	.mdr_load(mdr_load),
-	.mdr_en(mdr_en),
 	.ram_load(ram_load),
 	.ram_enh(ram_enh),
 	.ram_enl(ram_enl),
 	.call(call),
 	.ret(ret),
-
-	// Inout
-	.bus(bus)
+	.bus(bus),
+	.out(mem_out)
 );
 
 wire a_load;
 wire a_en;
 wire a_inc;
 wire a_dec;
-wire[7:0] a_val;
+wire[7:0] a_out;
 register reg_a(
-	// In
 	.clk(clk),
+	.rst(rst),
 	.load(a_load),
-	.en(a_en),
 	.inc(a_inc),
 	.dec(a_dec),
-
-	// Inout
 	.bus(bus),
-
-	// Out
-	.out(a_val)
+	.out(a_out)
 );
 
 wire b_load;
 wire b_en;
 wire b_inc;
 wire b_dec;
-wire[7:0] b_val;
+wire[7:0] b_out;
 register reg_b(
-	// In
 	.clk(clk),
+	.rst(rst),
 	.load(b_load),
-	.en(b_en),
 	.inc(b_inc),
 	.dec(b_dec),
-
-	// Inout
 	.bus(bus),
-
-	// Out
-	.out(b_val)
+	.out(b_out)
 );
 
 wire c_load;
 wire c_en;
 wire c_inc;
 wire c_dec;
-wire[7:0] c_val;
+wire[7:0] c_out;
 register reg_c(
-	// In
 	.clk(clk),
+	.rst(rst),
 	.load(c_load),
-	.en(c_en),
 	.inc(c_inc),
 	.dec(c_dec),
-
-	// Inout
 	.bus(bus),
-
-	// Out
-	.out(c_val)
+	.out(c_out)
 );
 
 wire[2:0] alu_op;
 wire alu_load;
 wire alu_en;
+wire[7:0] alu_out;
 alu alu(
-	// In
 	.clk(clk),
-	.a(a_val),
+	.rst(rst),
+	.a(a_out),
 	.load(alu_load),
 	.op(alu_op),
-	.en(alu_en),
-
-	// Out
-	.bus(bus)
+	.bus(bus),
+	.out(alu_out)
 );
 
-wire[1:0] flags_val;
+wire[1:0] flags_out;
 wire flags_lda;
 wire flags_ldb;
 wire flags_ldc;
 flags flags(
-	// In
 	.clk(clk),
-	.a(a_val),
-	.b(b_val),
-	.c(c_val),
+	.rst(rst),
+	.a(a_out),
+	.b(b_out),
+	.c(c_out),
 	.load_a(flags_lda),
 	.load_b(flags_ldb),
 	.load_c(flags_ldc),
-
-	// Out
-	.out(flags_val)
+	.out(flags_out)
 );
 
 controller controller(
 	.clk(clk),
-	.instr(ir_instr),
-	.flags(flags_val),
-	.ctrl_word({
+	.rst(rst),
+	.opcode(ir_out),
+	.flags(flags_out),
+	.out({
 		hlt,
-		a_load,
-		a_en,
-		a_inc,
-		a_dec,
-		b_load,
-		b_en,
-		b_inc,
-		b_dec,
-		c_load,
-		c_en,
-		c_inc,
-		c_dec,
-		flags_lda,
-		flags_ldb,
-		flags_ldc,
-		alu_op,
-		alu_load,
-		alu_en,
+		a_load, a_en, a_inc, a_dec,
+		b_load, b_en, b_inc, b_dec,
+		c_load, c_en, c_inc, c_dec,
+		flags_lda, flags_ldb, flags_ldc,
+		alu_op, alu_load, alu_en,
 		ir_load,
-		pc_inc,
-		pc_load,
-		pc_en,
-		mar_loadh,
-		mar_loadl,
-		mdr_load,
+		pc_inc, pc_load, pc_en,
+		mar_loadh, mar_loadl, mdr_load,
 		mdr_en,
-		ram_load,
-		ram_enh,
-		ram_enl,
-		call,
-		ret})
+		ram_load, ram_enh, ram_enl,
+		call, ret})
 );
 
 endmodule
diff --git a/src/sap2/top_tb.v b/src/sap2/top_tb.v
index 831e44c..5a054fe 100644
--- a/src/sap2/top_tb.v
+++ b/src/sap2/top_tb.v
@@ -4,8 +4,29 @@ module top_tb();
 initial begin
 	$dumpfile("top_tb.vcd");
 	$dumpvars(0, top_tb);
+	rst = 1;
+	#1 rst = 0;
 end
 
+reg[15:0] bus;
+
+always @(*) begin
+	if (a_en) begin
+		bus = a_out;
+	end else if (b_en) begin
+		bus = b_out;
+	end else if (c_en) begin
+		bus = c_out;
+	end else if (alu_en) begin
+		bus = alu_out;
+	end else if (pc_en) begin
+		bus = pc_out;
+	end else if (mdr_en) begin
+		bus = mem_out;
+	end else begin
+		bus = 16'b0;
+	end
+end
 
 reg clk_in = 0;
 integer i;
@@ -15,49 +36,36 @@ initial begin
 	end
 end
 
-
+reg rst;
 wire hlt;
-wire clr = 0;
-wire[15:0] bus;
-
 wire clk;
 clock clock(
-	// In
 	.hlt(hlt),
 	.clk_in(clk_in),
-
-	// Out
 	.clk_out(clk)
 );
 
 wire pc_inc;
 wire pc_load;
 wire pc_en;
+wire[15:0] pc_out;
 pc pc(
-	// In
 	.clk(clk),
-	.clr(clr),
+	.rst(rst),
 	.inc(pc_inc),
 	.load(pc_load),
-	.en(pc_en),
-
-	// Output
-	.bus(bus)
+	.bus(bus),
+	.out(pc_out)
 );
 
 wire ir_load;
-wire[7:0] ir_val;
+wire[7:0] ir_out;
 ir ir(
-	// In
 	.clk(clk),
-	.clr(clr),
+	.rst(rst),
 	.load(ir_load),
-
-	// Inout
 	.bus(bus),
-
-	// Out
-	.out(ir_val)
+	.out(ir_out)
 );
 
 wire mar_loadh;
@@ -69,153 +77,115 @@ wire ram_enh;
 wire ram_enl;
 wire call;
 wire ret;
+wire[15:0] mem_out;
 memory mem(
-	// In
 	.clk(clk),
+	.rst(rst),
 	.mar_loadh(mar_loadh),
 	.mar_loadl(mar_loadl),
 	.mdr_load(mdr_load),
-	.mdr_en(mdr_en),
 	.ram_load(ram_load),
 	.ram_enh(ram_enh),
 	.ram_enl(ram_enl),
 	.call(call),
 	.ret(ret),
-
-	// Inout
-	.bus(bus)
+	.bus(bus),
+	.out(mem_out)
 );
 
 wire a_load;
 wire a_en;
 wire a_inc;
 wire a_dec;
-wire[7:0] a_val;
+wire[7:0] a_out;
 register reg_a(
-	// In
 	.clk(clk),
+	.rst(rst),
 	.load(a_load),
-	.en(a_en),
 	.inc(a_inc),
 	.dec(a_dec),
-
-	// Inout
 	.bus(bus),
-
-	// Out
-	.out(a_val)
+	.out(a_out)
 );
 
 wire b_load;
 wire b_en;
 wire b_inc;
 wire b_dec;
-wire[7:0] b_val;
+wire[7:0] b_out;
 register reg_b(
-	// In
 	.clk(clk),
+	.rst(rst),
 	.load(b_load),
-	.en(b_en),
 	.inc(b_inc),
 	.dec(b_dec),
-
-	// Inout
 	.bus(bus),
-
-	// Out
-	.out(b_val)
+	.out(b_out)
 );
 
 wire c_load;
 wire c_en;
 wire c_inc;
 wire c_dec;
-wire[7:0] c_val;
+wire[7:0] c_out;
 register reg_c(
-	// In
 	.clk(clk),
+	.rst(rst),
 	.load(c_load),
-	.en(c_en),
 	.inc(c_inc),
 	.dec(c_dec),
-
-	// Inout
 	.bus(bus),
-
-	// Out
-	.out(c_val)
+	.out(c_out)
 );
 
 wire[2:0] alu_op;
 wire alu_load;
 wire alu_en;
+wire[7:0] alu_out;
 alu alu(
-	// In
 	.clk(clk),
-	.a(a_val),
+	.rst(rst),
+	.a(a_out),
 	.load(alu_load),
 	.op(alu_op),
-	.en(alu_en),
-
-	// Inout
-	.bus(bus)
+	.bus(bus),
+	.out(alu_out)
 );
 
-wire[1:0] flags_val;
+wire[1:0] flags_out;
 wire flags_lda;
 wire flags_ldb;
 wire flags_ldc;
 flags flags(
-	// In
 	.clk(clk),
-	.a(a_val),
-	.b(b_val),
-	.c(c_val),
+	.rst(rst),
+	.a(a_out),
+	.b(b_out),
+	.c(c_out),
 	.load_a(flags_lda),
 	.load_b(flags_ldb),
 	.load_c(flags_ldc),
-
-	// Out
-	.out(flags_val)
+	.out(flags_out)
 );
 
 controller controller(
 	.clk(clk),
-	.instr(ir_val),
-	.flags(flags_val),
-	.ctrl_word({
+	.rst(rst),
+	.opcode(ir_out),
+	.flags(flags_out),
+	.out({
 		hlt,
-		a_load,
-		a_en,
-		a_inc,
-		a_dec,
-		b_load,
-		b_en,
-		b_inc,
-		b_dec,
-		c_load,
-		c_en,
-		c_inc,
-		c_dec,
-		flags_lda,
-		flags_ldb,
-		flags_ldc,
-		alu_op,
-		alu_load,
-		alu_en,
+		a_load, a_en, a_inc, a_dec,
+		b_load, b_en, b_inc, b_dec,
+		c_load, c_en, c_inc, c_dec,
+		flags_lda, flags_ldb, flags_ldc,
+		alu_op, alu_load, alu_en,
 		ir_load,
-		pc_inc,
-		pc_load,
-		pc_en,
-		mar_loadh,
-		mar_loadl,
-		mdr_load,
+		pc_inc, pc_load, pc_en,
+		mar_loadh, mar_loadl, mdr_load,
 		mdr_en,
-		ram_load,
-		ram_enh,
-		ram_enl,
-		call,
-		ret})
+		ram_load, ram_enh, ram_enl,
+		call, ret})
 );
 
 endmodule