add fsm_traffic

.gitignore

@@ -0,0 +1,3 @@
+*.vcd
+*.vvp
+*.json

counter/counter.v

@@ -0,0 +1,18 @@
+/*
+    Contador
+*/
+
+module counter #(parameter N = 8) (
+    input clk,
+    input rst,
+    input write,
+    input [N-1:0] write_value,
+    output reg [N-1:0] count
+);
+
+    always @(posedge clk or posedge rst) begin
+        if (rst) count <= 0;
+        else if (write) count <= write_value;
+        else count <= count + 1; 
+    end
+endmodule

counter/counter_tb.v

@@ -0,0 +1,44 @@
+`include "./counter/counter.v"
+
+module counter_tb;
+    reg clk, rst, write_enable;
+    reg [15:0] write_value;
+    wire [15:0] count;
+
+    counter #(.N(16)) cnt(
+        .clk(clk),
+        .rst(rst),
+        .write(write_enable),
+        .write_value(write_value),
+        .count(count)
+    );
+
+    initial clk = 0;
+    always #5 clk = ~clk;
+
+    initial begin
+        $dumpfile("./counter/counter.vcd");
+        $dumpvars(0, counter_tb);
+
+        rst = 1; write_enable = 0; write_value = 0;
+        @(posedge clk); #1
+        rst = 0;
+
+        // Contar 20 ciclos
+        repeat(20) @(posedge clk);
+        #1 $display("despues de 20 ciclos: count=%0d", count);
+
+        // Load a 200
+        write_enable = 1; write_value = 200;
+        @(posedge clk); #1
+        write_enable = 0;
+        $display("tras load 200: count=%0d", count);
+
+        // Contar hasta overflow (56 ciclos llega a 255 y desborda a 0)
+        repeat(60) @(posedge clk);
+        #1 $display("tras 60 ciclos mas: count=%0d", count);
+
+        $finish;
+    end
+
+endmodule

decoder_encoder/decoder_encoder.v

@@ -0,0 +1,30 @@
+/*
+    Decoder / Encoder
+*/
+
+module decoder_3bit (
+    input [2:0] in,
+    output [7:0] out
+);
+    assign out = 1 << in;
+endmodule
+
+module encoder_3bit(
+    input [7:0] in,
+    output reg [2:0] out
+);
+    always @(*) begin
+        out = 0;
+
+        casez(in) 
+            8'b1???????: out = 3'd7;
+            8'b01??????: out = 3'd6;
+            8'b001?????: out = 3'd5;
+            8'b0001????: out = 3'd4;
+            8'b00001???: out = 3'd3;
+            8'b000001??: out = 3'd2;
+            8'b0000001?: out = 3'd1;
+            8'b00000001: out = 3'd0;
+        endcase
+    end
+endmodule

decoder_encoder/decoder_encoder_tb.v

@@ -0,0 +1,38 @@
+`include "./decoder_encoder/decoder_encoder.v"
+
+module decoder_3bit_tb;
+    reg [2:0] in;
+    wire [7:0] out;
+    wire [2:0] encoded;
+
+    decoder_3bit dec(
+        .in(in),
+        .out(out)
+    ); 
+
+    encoder_3bit enc(
+        .in(out),
+        .out(encoded)
+    );
+
+    initial begin
+        $dumpfile("./decoder_encoder/decoder_encoder.vcd");
+        $dumpvars(0, decoder_3bit_tb);
+
+        in = 3'b000;
+        #1
+        $display("in=%d, out=%b, enc=%d", in, out, encoded);
+        in = 3'b001;
+        #1
+        $display("in=%d, out=%b, enc=%d", in, out, encoded);
+        in = 3'b010;
+        #1
+        $display("in=%d, out=%b, enc=%d", in, out, encoded);
+        in = 3'b100;
+        #1
+        $display("in=%d, out=%b, enc=%d", in, out, encoded);
+        in = 3'b111;
+        #1
+        $display("in=%d, out=%b, enc=%d", in, out, encoded);
+    end
+endmodule

flip_flop/flip_flop.v

@@ -0,0 +1,17 @@
+/*
+    Flip-Flop D y registro
+*/
+
+module register #(parameter N = 8)(
+    input clk,
+    input rst,
+    input en,
+    input [N-1:0] d,
+    output reg [N-1:0] q
+);
+    always @(posedge clk or posedge rst) begin
+        if (rst) q <= 0;
+        else if (en) q <= d;
+    end
+
+endmodule

flip_flop/flip_flop_tb.v

@@ -0,0 +1,52 @@
+/*
+    Flip-Flop D y registro
+*/
+`include "./flip_flop/flip_flop.v"
+
+module register_tb;
+    reg clk, rst, en;
+    reg [7:0] d;
+    wire [7:0] q;
+
+    register #(.N(8)) dut (
+        .clk(clk),
+        .rst(rst),
+        .en(en),
+        .d(d),
+        .q(q)
+    );
+
+    initial clk = 0;
+    always #5 clk = ~clk;
+
+    initial begin
+        $dumpfile("./flip_flop/flip_flop.vcd");
+        $dumpvars(0, register_tb);
+
+        rst = 1; en = 0; d = 0;
+        @(posedge clk); #1
+
+        rst = 0;
+        @(posedge clk); #1
+        $display("rst=0, en=0, d=%0d, q=%0d (q no cambia)", d, q);
+
+        en = 1; d = 8'd42;
+        @(posedge clk); #1
+        $display("en=1, d=42 → q=%0d", q);
+
+        d = 8'd99;
+        @(posedge clk); #1
+        $display("en=1, d=99 → q=%0d", q);
+
+        en = 0; d = 8'd7;
+        @(posedge clk); #1
+        $display("en=0, d=7  → q=%0d (q mantiene 99)", q);
+
+        rst = 1;
+        @(posedge clk); #1
+        $display("rst=1      → q=%0d (q=0)", q);
+
+        $finish;
+    end
+
+endmodule

fsm_traffic/fsm_traffic.v

@@ -0,0 +1,48 @@
+/*
+    fsm_traffic
+*/
+module fsm_traffic (
+    input clk,
+    input rst,
+    output red_led,
+    output green_led,
+    output yellow_led
+);
+    localparam RED      = 2'b00;
+    localparam GREEN    = 2'b01;
+    localparam YELLOW   = 2'b10;
+
+    reg[1:0] state, next_state;
+    reg[7:0] timer;
+
+    always @(posedge clk or posedge rst) begin
+       if (rst) begin
+        state <= RED;
+        timer <= 3;
+       end
+       else if (timer == 0) begin
+            state <= next_state;
+
+            case (next_state)
+                RED:     timer <= 3;
+                YELLOW:  timer <= 1;
+                GREEN:   timer <= 2;
+                default: timer <= 3;
+            endcase
+       end
+       else timer <= timer - 1; 
+    end
+
+    always @(*) begin
+        case (state)
+            RED:     next_state = GREEN;
+            YELLOW:  next_state = RED;
+            GREEN:   next_state = YELLOW;
+            default: next_state = RED;
+        endcase
+    end
+
+    assign red_led = state == RED;
+    assign green_led = state == GREEN;
+    assign yellow_led = state == YELLOW;
+endmodule

fsm_traffic/fsm_traffic_tb.v

@@ -0,0 +1,56 @@
+/*
+    fsm_traffic testbench
+*/
+`include "fsm_traffic/fsm_traffic.v"
+
+module fsm_traffic_tb;
+    reg clk, rst;
+    wire red_led, green_led, yellow_led;
+
+    fsm_traffic dut (
+        .clk(clk),
+        .rst(rst),
+        .red_led(red_led),
+        .green_led(green_led),
+        .yellow_led(yellow_led)
+    );
+
+    initial clk = 0;
+    always #5 clk = ~clk;
+
+    task show_state;
+        $display("t=%0t | rst=%b | R=%b G=%b Y=%b",
+            $time, rst, red_led, green_led, yellow_led);
+    endtask
+
+    initial begin
+        $dumpfile("fsm_traffic/fsm_traffic.vcd");
+        $dumpvars(0, fsm_traffic_tb);
+
+        // Reset
+        rst = 1;
+        @(posedge clk); #1
+        show_state;
+
+        rst = 0;
+
+        // Dejar correr varios ciclos para ver todos los estados
+        repeat(9) begin
+            @(posedge clk); #1
+            show_state;
+        end
+
+        // Reset a mitad de secuencia — debe volver a RED
+        rst = 1;
+        @(posedge clk); #1
+        show_state;
+        rst = 0;
+
+        repeat(3) begin
+            @(posedge clk); #1
+            show_state;
+        end
+
+        $finish;
+    end
+endmodule

mux_demux/mux_demux.v

@@ -32,3 +32,94 @@ module demux_1n2 #(parameter N = 8) (
     assign a = sel ? 0 : in;
     assign b = sel ? in : 0;
 endmodule
+
+module mux_4n1 #(parameter N = 8) (
+    input [N-1:0] a,
+    input [N-1:0] b,
+    input [N-1:0] c,
+    input [N-1:0] d,
+    input [1:0] sel,
+    output reg [N-1:0] out
+);
+
+    always @(*) begin
+        case (sel)
+            2'b00: out = a;
+            2'b01: out = b;
+            2'b10: out = c;
+            2'b11: out = d;
+            default: out = a;
+        endcase
+    end
+endmodule
+
+module demux_1n4 #(parameter N = 8) (
+    input [N-1:0] in,
+    input [1:0] sel,
+    output reg [N-1:0] a,
+    output reg [N-1:0] b,
+    output reg [N-1:0] c,
+    output reg [N-1:0] d
+);
+    always @(*) begin
+        a = 0; b = 0; c = 0; d = 0;
+
+        case (sel)
+            2'b00: a = in;
+            2'b01: b = in;
+            2'b10: c = in;
+            2'b11: d = in;
+            default: a = in;
+        endcase
+    end
+endmodule
+
+module mux_8n1 #(parameter N = 8) (
+    input [N-1:0] a,
+    input [N-1:0] b,
+    input [N-1:0] c,
+    input [N-1:0] d,
+    input [N-1:0] e,
+    input [N-1:0] f,
+    input [N-1:0] g,
+    input [N-1:0] h,
+    input [2:0] sel,
+    output reg [N-1:0] out
+);
+
+    always @(*) begin
+        case (sel)
+            3'b000: out = a;
+            3'b001: out = b;
+            3'b010: out = c;
+            3'b011: out = d;
+            3'b100: out = e;
+            3'b101: out = f;
+            3'b110: out = g;
+            3'b111: out = h;
+            default: out = a;
+        endcase
+    end
+endmodule
+
+module mux_Nn1 #(
+    parameter DATA_W = 8, // bits por dato
+    parameter SEL_W = 3   // bits de sel -> 2^SEL_W entradas
+)(
+    input [(1<<SEL_W) * DATA_W - 1 : 0] in,
+    input [SEL_W-1:0] sel,
+    output [DATA_W-1:0] out
+);
+    localparam INPUTS = 1 << SEL_W; // 2^3 = 8
+
+    wire [DATA_W-1:0] data [0:INPUTS-1];
+
+    genvar i;
+    generate
+        for (i=0; i<INPUTS; i = i + 1) begin: unpack
+            assign data[i] = in[i * DATA_W +: DATA_W];
+        end
+    endgenerate
+
+    assign out = data[sel];
+endmodule

mux_demux/mux_demux_tb.v

@@ -0,0 +1,43 @@
+`include "./mux_demux/mux_demux.v"
+
+module mux_demux_tb();
+    reg [7:0] a, b;
+    reg sel;
+
+    wire [7:0] out, _a, _b;
+
+    mux_Nn1 #(.DATA_W(8), .SEL_W(1)) mux (
+        .in({b, a}),
+        .sel(sel),
+        .out(out)
+    );
+
+    demux_1n2 demux (
+        .in(out),
+        .sel(sel),
+        .a(_a),
+        .b(_b)
+    );
+
+    initial begin
+        $dumpfile("./mux_demux/mux_demux.vcd");
+        $dumpvars(0, mux_demux_tb);
+
+        a = 20; b = 5; sel = 0;
+        #1
+        $display("a=%d, b=%d, sel=%b out=%d _a=%d, _b=%d", a, b, sel, out, _a, _b);
+        a = 21; b = 5; sel = 0;
+        #1
+        $display("a=%d, b=%d, sel=%b out=%d _a=%d, _b=%d", a, b, sel, out, _a, _b);
+        a = 22; b = 5; sel = 0;
+        #1
+        $display("a=%d, b=%d, sel=%b out=%d _a=%d, _b=%d", a, b, sel, out, _a, _b);
+        a = 22; b = 5; sel = 1;
+        #1
+        $display("a=%d, b=%d, sel=%b out=%d _a=%d, _b=%d", a, b, sel, out, _a, _b);
+        a = 22; b = 15; sel = 1;
+        #1
+        $display("a=%d, b=%d, sel=%b out=%d _a=%d, _b=%d", a, b, sel, out, _a, _b);
+
+    end
+endmodule

ram/ram.v

@@ -0,0 +1,24 @@
+/*
+    Ram Sincrona
+*/
+
+module ram #(
+    parameter DEPTH = 256, // posiciones
+    parameter W     = 16   // bits por posicion
+) (
+    input                       clk,
+    input                       wr_en,
+    input [$clog2(DEPTH)-1:0]   addr,
+    input [W-1:0]               wr_data,
+    output reg [W-1:0]          rd_data
+);
+    reg [W-1:0] mem [0:DEPTH-1];
+
+    always @(posedge clk) begin
+        if (wr_en)
+            mem[addr] <= wr_data;
+        else
+            rd_data <= mem[addr];
+    end
+
+endmodule

ram/ram_tb.v

@@ -0,0 +1,54 @@
+/*
+    Ram Sincrona testbench
+*/
+`include "ram/ram.v"
+
+module ram_tb;
+    reg clk, wr_en;
+    reg [7:0]   addr;
+    reg [15:0]  wr_data;
+    wire [15:0] rd_data;
+
+    ram ram1(
+        .clk(clk),
+        .wr_en(wr_en),
+        .addr(addr),
+        .wr_data(wr_data),
+        .rd_data(rd_data)
+    );
+
+    initial clk = 0;
+    always #5 clk = ~clk;
+
+    initial begin
+        $dumpfile("ram/ram.vcd");
+        $dumpvars(0, ram_tb);
+
+        wr_en = 0; addr = 0; wr_data = 0;
+        @(posedge clk);
+        $display("wr_en=%b, addr=%d, wr_data=%d, rd_data=%d", wr_en, addr, wr_data, rd_data);
+
+        wr_en = 1; addr = 25; wr_data = 256;
+        @(posedge clk);
+        $display("wr_en=%b, addr=%d, wr_data=%d, rd_data=%d", wr_en, addr, wr_data, rd_data);
+
+        wr_en = 0;
+        @(posedge clk);
+        $display("wr_en=%b, addr=%d, wr_data=%d, rd_data=%d", wr_en, addr, wr_data, rd_data);
+
+        @(posedge clk);
+        $display("wr_en=%b, addr=%d, wr_data=%d, rd_data=%d", wr_en, addr, wr_data, rd_data);
+
+        addr = 16;
+
+        @(posedge clk);
+        $display("wr_en=%b, addr=%d, wr_data=%d, rd_data=%d", wr_en, addr, wr_data, rd_data);
+
+        @(posedge clk);
+        $display("wr_en=%b, addr=%d, wr_data=%d, rd_data=%d", wr_en, addr, wr_data, rd_data);
+
+
+        $finish;
+    end
+    
+endmodule

register_file/register_file.v

@@ -0,0 +1,38 @@
+/*
+    Registros
+*/
+
+module register_file #(
+    parameter REGS = 16,
+    parameter W    = 16
+) (
+    input                       clk,
+    input                       rst,
+    // Puerto escritura
+    input [$clog2(REGS)-1:0]    wr_addr,
+    input [W-1:0]               wr_data,
+    input                       wr_en,
+    // Puerto lectura 1
+    input [$clog2(REGS)-1:0]    rd_addr1,
+    output [W-1:0]              rd_data1,
+    // Puerto lectura 2
+    input [$clog2(REGS)-1:0]    rd_addr2,
+    output [W-1:0]              rd_data2
+);
+    reg [W-1:0] regs [0:REGS-1];
+
+    // Lectura combinacional
+    assign rd_data1 = regs[rd_addr1];
+    assign rd_data2 = regs[rd_addr2];
+
+    // Escritura sincrona
+    integer i;
+    always @(posedge clk or posedge rst) begin
+       if (rst) begin
+        for (i = 0; i < REGS; i = i + 1)
+            regs[i] <= 0;
+       end else if (wr_en) begin
+            regs[wr_addr] <= wr_data;
+       end
+    end
+endmodule

register_file/register_file_tb.v

@@ -0,0 +1,60 @@
+/*
+    Registros
+*/
+`include "./register_file/register_file.v"
+module register_file_tb;
+    reg clk, rst, wr_en;
+    reg [3:0] wr_addr;
+    reg [15:0] wr_data;
+    reg [3:0] rd_addr1, rd_addr2;
+    wire [15:0] rd_value1, rd_value2;
+
+    register_file register(
+        .clk(clk),
+        .rst(rst),
+        .wr_addr(wr_addr),
+        .wr_data(wr_data),
+        .wr_en(wr_en),
+        .rd_addr1(rd_addr1),
+        .rd_data1(rd_value1),
+        .rd_addr2(rd_addr2),
+        .rd_data2(rd_value2)
+    );
+
+    initial clk = 0;
+    always #5 clk = ~clk;
+
+    initial begin
+        $dumpfile("register_file/register_file.vcd");
+        $dumpvars(0, register_file_tb);
+
+        rst = 1; wr_en = 0; wr_addr = 0; wr_data = 0;
+        rd_addr1 = 0; rd_addr2 = 0;
+        @(posedge clk);
+        $display("rst=%b, wr_en=%b, wr_add=%d, wr_data=%d", rst, wr_en, wr_addr, wr_data);
+        $display("rd_addr1=%d, rd_addr2=%d, rd_value1=%d, rd_value2=%d", rd_addr1, rd_addr2, rd_value1, rd_value2);
+
+        rst = 0;
+        @(posedge clk);
+        $display("rst=%b, wr_en=%b, wr_add=%d, wr_data=%d", rst, wr_en, wr_addr, wr_data);
+        $display("rd_addr1=%d, rd_addr2=%d, rd_value1=%d, rd_value2=%d", rd_addr1, rd_addr2, rd_value1, rd_value2);
+
+        wr_en = 1; wr_addr = 1; wr_data = 16'hBEEF;
+        @(posedge clk);
+        $display("rst=%b, wr_en=%b, wr_add=%d, wr_data=%d", rst, wr_en, wr_addr, wr_data);
+        $display("rd_addr1=%d, rd_addr2=%d, rd_value1=%d, rd_value2=%d", rd_addr1, rd_addr2, rd_value1, rd_value2);
+
+        wr_en = 0;
+        @(posedge clk);
+        $display("rst=%b, wr_en=%b, wr_add=%d, wr_data=%d", rst, wr_en, wr_addr, wr_data);
+        $display("rd_addr1=%d, rd_addr2=%d, rd_value1=%d, rd_value2=%d", rd_addr1, rd_addr2, rd_value1, rd_value2);
+
+        rd_addr1 = 1;
+        @(posedge clk);
+        $display("rst=%b, wr_en=%b, wr_add=%d, wr_data=%d", rst, wr_en, wr_addr, wr_data);
+        $display("rd_addr1=%d, rd_addr2=%d, rd_value1=%d, rd_value2=%d", rd_addr1, rd_addr2, rd_value1, rd_value2);
+
+        repeat(100) @(posedge clk);
+        $finish;
+    end
+endmodule

roadmap.md

@@ -345,16 +345,16 @@ gtkwave modulo.vcd
 - [x] Fase 1.1 — Full Adder
 - [x] Fase 1.2 — Adder N bits
 - [x] Fase 1.3 — ALU basica
-- [ ] Fase 1.4 — Mux / Demux
+- [x] Fase 1.4 — Mux / Demux
-- [ ] Fase 1.5 — Decoder / Encoder
+- [x] Fase 1.5 — Decoder / Encoder
-- [ ] Fase 2.1 — Flip-Flop D y registro
+- [x] Fase 2.1 — Flip-Flop D y registro
-- [ ] Fase 2.2 — Contador
+- [x] Fase 2.2 — Contador
-- [ ] Fase 2.3 — Shift Register
+- [x] Fase 2.3 — Shift Register
-- [ ] Fase 2.4 — Register File
+- [x] Fase 2.4 — Register File
-- [ ] Fase 3.1 — RAM sincrona
+- [x] Fase 3.1 — RAM sincrona
-- [ ] Fase 3.2 — ROM
+- [x] Fase 3.2 — ROM
-- [ ] Fase 3.3 — Stack
+- [x] Fase 3.3 — Stack
-- [ ] Fase 4.1 — FSM Semaforo
+- [x] Fase 4.1 — FSM Semaforo
 - [ ] Fase 4.2 — UART TX
 - [ ] Fase 5.1 — Fetch Unit
 - [ ] Fase 5.2 — Decoder de instrucciones

rom/program.hex

@@ -0,0 +1,5 @@
+BEEF
+1234
+ABCD
+0000
+FF00

rom/rom.v

@@ -0,0 +1,21 @@
+/*
+    ROM
+*/
+
+module rom #(
+    parameter DEPTH = 256,
+    parameter W     = 16,
+    parameter FILE  = ""
+) (
+    input                       clk,
+    input [$clog2(DEPTH)-1:0]   addr,
+    output reg [W-1:0]          rd_data
+);
+    reg [W-1:0] mem [0:DEPTH-1];
+
+    initial $readmemh(FILE, mem);
+
+    always @(posedge clk) begin
+        rd_data <= mem[addr];        
+    end
+endmodule

rom/rom_tb.v

@@ -0,0 +1,44 @@
+/*
+    ROM
+*/
+`include "rom/rom.v"
+
+module rom_tb;
+    reg clk;
+    reg [7:0]   addr;
+    wire [15:0] rd_data;
+
+    rom #(.FILE("rom/program.hex")) rom1(
+        .clk(clk),
+        .addr(addr),
+        .rd_data(rd_data)
+    );
+
+    initial clk = 0;
+    always #5 clk = ~clk;
+
+    initial begin
+        $dumpfile("rom/rom.vcd");
+        $dumpvars(0, rom_tb);
+
+        addr = 0;
+        @(posedge clk);
+        $display("addr=%d, rd_data=%x", addr, rd_data);
+        @(posedge clk);
+        $display("addr=%d, rd_data=%x", addr, rd_data);
+
+        addr = 1;
+        @(posedge clk);
+        $display("addr=%d, rd_data=%x", addr, rd_data);
+        @(posedge clk);
+        $display("addr=%d, rd_data=%x", addr, rd_data);
+
+        addr = 2;
+        @(posedge clk);
+        $display("addr=%d, rd_data=%x", addr, rd_data);
+        @(posedge clk);
+        $display("addr=%d, rd_data=%x", addr, rd_data);
+        
+        $finish;
+    end
+endmodule

run.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+
+if [ -z "$1" ]; then
+    echo "Usage: $0 <module>"
+    exit 1
+fi
+
+module="${1#./}"
+module="${module#/}"
+module="${module%/}"
+
+iverilog -o "./$module/$module.vvp" "./$module/${module}_tb.v" || exit 1
+
+vvp "./$module/$module.vvp" || exit 1
+
+surfer "./$module/$module.vcd"

shift_register/shift_register.v

@@ -0,0 +1,24 @@
+module shift_register #(parameter N = 8) (
+    input clk,
+    input rst,
+    input load,
+    input shift_en,
+    input dir,
+    input serial_in,
+    input [N-1:0] parallel_in,
+    output reg [N-1:0] q,
+    output serial_out
+);
+
+    assign serial_out = dir ? q[0] : q[N-1];
+
+    always @(posedge clk or posedge rst) begin
+        if (rst) q <= 0;
+        else if (load) q <= parallel_in;
+        else if (shift_en) begin
+            if (dir == 0) q <= {q[N-2:0], serial_in};
+            else q <= {serial_in, q[N-1:1]};
+        end
+    end
+
+endmodule

shift_register/shift_register_tb.v

@@ -0,0 +1,48 @@
+`include "./shift_register/shift_register.v"
+
+module shift_register_tb;
+    reg clk, rst, load, shift_en, dir, serial_in;
+    reg [7:0] parallel_in;
+    wire [7:0] q;
+    wire serial_out;
+
+    shift_register register(
+        .clk(clk),
+        .rst(rst),
+        .load(load),
+        .shift_en(shift_en),
+        .dir(dir),
+        .serial_in(serial_in),
+        .parallel_in(parallel_in),
+        .q(q),
+        .serial_out(serial_out)
+    );
+
+    initial clk = 0;
+    always #5 clk = ~clk;
+
+    initial begin
+        $dumpfile("./shift_register/shift_register.vcd");
+        $dumpvars(0, shift_register_tb);
+
+        rst = 1; load = 0; shift_en = 1; dir = 0; serial_in = 0;
+        @(posedge clk);
+
+        $display("rst=%b, load=%b, shift_en=%b, dir=%b, serial_in=%b, q=%b", rst, load, shift_en, dir, serial_in, q);
+
+        rst = 0; load = 1; parallel_in = 64;
+        @(posedge clk);
+
+        $display("rst=%b, load=%b, shift_en=%b, dir=%b, serial_in=%b, q=%b", rst, load, shift_en, dir, serial_in, q);
+
+        load = 0; serial_in = 1;
+        @(posedge clk);
+        $display("rst=%b, load=%b, shift_en=%b, dir=%b, serial_in=%b, q=%b", rst, load, shift_en, dir, serial_in, q);
+
+        repeat(10) @(posedge clk);
+        $display("rst=%b, load=%b, shift_en=%b, dir=%b, serial_in=%b, q=%b", rst, load, shift_en, dir, serial_in, q);
+
+        $finish;
+    end
+
+endmodule

stack/stack.v

@@ -0,0 +1,33 @@
+/*
+    Stack
+*/
+
+module stack #(
+    parameter DEPTH = 256,
+    parameter W     = 16
+) (
+    input               clk,
+    input               rst,
+    input               push,
+    input               pop,
+    input [W-1:0]       value,
+    output reg [W-1:0]  out
+);
+    reg [W-1:0] mem [0:DEPTH-1];
+    reg [$clog2(DEPTH):0] sp;  // bit extra para detectar overflow
+
+    wire full  = (sp == DEPTH);
+    wire empty = (sp == 0);
+
+    always @(posedge clk or posedge rst) begin
+        if (rst) begin
+            sp <= 0;
+        end else if (push && !full) begin
+            mem[sp] <= value;
+            sp <= sp + 1;
+        end else if (pop && !empty) begin
+            out <= mem[sp - 1];
+            sp <= sp - 1;
+        end
+    end
+endmodule

stack/stack_tb.v

@@ -0,0 +1,63 @@
+/*
+    Stack testbench
+*/
+
+`include "stack/stack.v"
+
+module stack_tb;
+    reg clk, rst, push, pop;
+    reg[15:0]   in;
+    wire [15:0] out;
+
+    stack stack1(
+        .clk(clk),
+        .rst(rst),
+        .push(push),
+        .pop(pop),
+        .value(in),
+        .out(out)
+    );
+
+    initial clk = 0;
+    always #5 clk = ~clk;
+
+    initial begin
+        $dumpfile("stack/stack.vcd");
+        $dumpvars(0, stack_tb);
+
+        rst = 1; push = 0; pop = 0; in = 0;
+        @(posedge clk); #1
+        rst = 0;
+        $display("push=%b, pop=%b, value=%x, out=%x", push, pop, in, out);
+
+        push = 1; pop = 0; in = 69;
+        @(posedge clk); #1
+        $display("push=%b, pop=%b, value=%x, out=%x", push, pop, in, out);
+
+        push = 1; pop = 0; in = 40;
+        @(posedge clk); #1
+        $display("push=%b, pop=%b, value=%x, out=%x", push, pop, in, out);
+
+        push = 0; pop = 0; in = 0;
+        @(posedge clk); #1
+        $display("push=%b, pop=%b, value=%x, out=%x", push, pop, in, out);
+
+        push = 0; pop = 1; in = 0;
+        @(posedge clk); #1
+        $display("push=%b, pop=%b, value=%x, out=%x", push, pop, in, out);
+        push = 0; pop = 0; in = 0;
+        @(posedge clk); #1
+        $display("push=%b, pop=%b, value=%x, out=%x", push, pop, in, out);
+
+
+        push = 0; pop = 1; in = 0;
+        @(posedge clk); #1 
+        $display("push=%b, pop=%b, value=%x, out=%x", push, pop, in, out);
+        push = 0; pop = 0; in = 0;
+        @(posedge clk); #1
+        $display("push=%b, pop=%b, value=%x, out=%x", push, pop, in, out);
+
+
+        $finish;
+    end
+endmodule