`timescale 1ns / 1ps
`default_nettype none

// -----------------------------------------------------------------------------
// cpu21_vga —— 640x480@60 的"格子"显示控制器（显存端口接板级顶层的双口 RAM）。
//
// CPU 不直接操作像素：它只通过 MMIO 往显示缓冲区里写"每格 1 字节"（字形 + 颜色），
// 本模块按像素扫描把格子展开成画面（8x8 字模放大 2 倍填满 16x16 的格子）。
// 这样一格只要 1 次字节写，刷屏开销极小。
//
// 网格：40 列 x 30 行，每格 16x16 像素 = 640x480。
//
// 时钟：本模块工作在 CPU 时钟（clk）下，用 tick（每 2 个 clk 一个使能）产生
// 25 MHz 的像素节拍。**不引入第二个时钟域**，因此显示缓冲区的读（本模块）
// 与写（MMIO，同一时钟）之间没有跨时钟域问题。
//
// 光标：由 CURSOR 寄存器的 (x,y) 决定，在对应格子上画一个白色闪动的方框
// （CTRL[0] 控制显示与否）。缓冲区字节的 bit7 在本模块中不使用（保留）。
// -----------------------------------------------------------------------------
module cpu21_vga #(
        parameter integer H_VISIBLE = 640,
        parameter integer H_FP      = 16,
        parameter integer H_SYNC    = 96,
        parameter integer H_BP      = 48,
        parameter integer V_VISIBLE = 480,
        parameter integer V_FP      = 10,
        parameter integer V_SYNC    = 2,
        parameter integer V_BP      = 33,
        parameter integer COLS      = 40,
        parameter integer ROWS      = 30
    ) (
        input  wire        clk,
        input  wire        reset,
        input  wire        tick,          // 25 MHz 像素使能（每 2 个 clk 一拍）
        // 显示缓冲区读端口
        output wire [ 9:0] fb_raddr_o,
        input  wire [31:0] fb_word_i,
        // 控制
        input  wire [31:0] ctrl_i,
        input  wire [31:0] cursor_i,
        // VGA 输出
        output reg  [ 3:0] vga_r,
        output reg  [ 3:0] vga_g,
        output reg  [ 3:0] vga_b,
        output reg         vga_hs,
        output reg         vga_vs,
        output reg         frame_tick_o
    );

    localparam integer H_TOTAL = H_VISIBLE + H_FP + H_SYNC + H_BP;  // 800
    localparam integer V_TOTAL = V_VISIBLE + V_FP + V_SYNC + V_BP;  // 525

    // ---------------------------------------------------------------------------
    // 扫描计数
    // ---------------------------------------------------------------------------
    reg [9:0] hx, vy;

    always @(posedge clk or posedge reset) begin
        if (reset) begin
            hx <= 10'd0;
            vy <= 10'd0;
        end
        else if (tick) begin
            if (hx == H_TOTAL - 1) begin
                hx <= 10'd0;
                vy <= (vy == V_TOTAL - 1) ? 10'd0 : (vy + 10'd1);
            end
            else begin
                hx <= hx + 10'd1;
            end
        end
    end

    wire de = (hx < H_VISIBLE) && (vy < V_VISIBLE);

    // 同步信号在 tick 上寄存输出
    wire hs_n = ~((hx >= (H_VISIBLE + H_FP)) && (hx < (H_VISIBLE + H_FP + H_SYNC)));
    wire vs_n = ~((vy >= (V_VISIBLE + V_FP)) && (vy < (V_VISIBLE + V_FP + V_SYNC)));

    // ---------------------------------------------------------------------------
    // 格子索引与缓冲区读出
    // ---------------------------------------------------------------------------
    wire [5:0] ccol = hx[9:4];   // 0..39
    wire [4:0] crow = vy[8:4];   // 0..29
    wire [10:0] cidx = (crow << 5) + (crow << 3) + ccol;  // row*40 + col

    assign fb_raddr_o = cidx[10:2];   // 字地址（1 字 = 4 格）

    wire [1:0]  lane = cidx[1:0];
    wire [31:0] cell_word = fb_word_i;
    wire [7:0]  cell_byte = cell_word >> {lane, 3'b000};

    wire [3:0] glyph = cell_byte[3:0];
    wire [2:0] gcolor = cell_byte[6:4];
    // 全局背景色（字模点为 0 时显示的颜色）
    wire [2:0] bgcolor = ctrl_i[7:4];

    // ---------------------------------------------------------------------------
    // 8x8 字模（bit7 = 最左像素），放大 2 倍填满 16x16 的格子
    // ---------------------------------------------------------------------------
    wire [2:0] fx = hx[3:1];
    wire [2:0] fy = vy[3:1];

    function [7:0] font_row;
        input [3:0] g;
        input [2:0] r;
        begin
            case (g)
                4'd0:
                    font_row = 8'h00;  // 空白
                4'd1:
                    font_row = (r == 3'd0) ? 8'h18 : (r == 3'd1) ? 8'h38 : (r == 3'd2) ? 8'h18 :
                                (r == 3'd3) ? 8'h18 : (r == 3'd4) ? 8'h18 : (r == 3'd5) ? 8'h18 :
                                            (r == 3'd6) ? 8'h7E : 8'h00;  // 1
                4'd2:
                    font_row = (r == 3'd0) ? 8'h3C : (r == 3'd1) ? 8'h66 : (r == 3'd2) ? 8'h06 :
                                (r == 3'd3) ? 8'h0C : (r == 3'd4) ? 8'h18 : (r == 3'd5) ? 8'h30 :
                                            (r == 3'd6) ? 8'h7E : 8'h00;  // 2
                4'd3:
                    font_row = (r == 3'd0) ? 8'h3C : (r == 3'd1) ? 8'h66 : (r == 3'd2) ? 8'h06 :
                                (r == 3'd3) ? 8'h1C : (r == 3'd4) ? 8'h06 : (r == 3'd5) ? 8'h66 :
                                            (r == 3'd6) ? 8'h3C : 8'h00;  // 3
                4'd4:
                    font_row = (r == 3'd0) ? 8'h0C : (r == 3'd1) ? 8'h1C : (r == 3'd2) ? 8'h3C :
                                (r == 3'd3) ? 8'h6C : (r == 3'd4) ? 8'h7E : (r == 3'd5) ? 8'h0C :
                                            (r == 3'd6) ? 8'h0C : 8'h00;  // 4
                4'd5:
                    font_row = (r == 3'd0) ? 8'h7E : (r == 3'd1) ? 8'h60 : (r == 3'd2) ? 8'h7C :
                                (r == 3'd3) ? 8'h06 : (r == 3'd4) ? 8'h06 : (r == 3'd5) ? 8'h66 :
                                            (r == 3'd6) ? 8'h3C : 8'h00;  // 5
                4'd6:
                    font_row = (r == 3'd0) ? 8'h1C : (r == 3'd1) ? 8'h30 : (r == 3'd2) ? 8'h60 :
                                (r == 3'd3) ? 8'h7C : (r == 3'd4) ? 8'h66 : (r == 3'd5) ? 8'h66 :
                                            (r == 3'd6) ? 8'h3C : 8'h00;  // 6
                4'd7:
                    font_row = (r == 3'd0) ? 8'h7E : (r == 3'd1) ? 8'h66 : (r == 3'd2) ? 8'h0C :
                                (r == 3'd3) ? 8'h18 : (r == 3'd4) ? 8'h18 : (r == 3'd5) ? 8'h18 :
                                            (r == 3'd6) ? 8'h18 : 8'h00;  // 7
                4'd8:
                    font_row = (r == 3'd0) ? 8'h3C : (r == 3'd1) ? 8'h66 : (r == 3'd2) ? 8'h66 :
                                (r == 3'd3) ? 8'h3C : (r == 3'd4) ? 8'h66 : (r == 3'd5) ? 8'h66 :
                                            (r == 3'd6) ? 8'h3C : 8'h00;  // 8
                4'd9:
                    font_row = (r == 3'd0) ? 8'hFF : (r == 3'd1) ? 8'h81 : (r == 3'd2) ? 8'hBD :
                                (r == 3'd3) ? 8'hA5 : (r == 3'd4) ? 8'hA5 : (r == 3'd5) ? 8'hBD :
                                            (r == 3'd6) ? 8'h81 : 8'hFF;  // 未揭开的方块
                4'd10:
                    font_row = (r == 3'd0) ? 8'h40 : (r == 3'd1) ? 8'h70 : (r == 3'd2) ? 8'h78 :
                                (r == 3'd3) ? 8'h70 : (r == 3'd4) ? 8'h40 : (r == 3'd5) ? 8'h40 :
                                            (r == 3'd6) ? 8'h40 : 8'h00;  // 旗
                4'd11:
                    font_row = (r == 3'd0) ? 8'h3C : (r == 3'd1) ? 8'h7E : (r == 3'd2) ? 8'hFF :
                                (r == 3'd3) ? 8'hFF : (r == 3'd4) ? 8'hFF : (r == 3'd5) ? 8'hFF :
                                            (r == 3'd6) ? 8'h7E : 8'h3C;  // 雷
                4'd12:
                    font_row = (r == 3'd0) ? 8'h81 : (r == 3'd1) ? 8'h42 : (r == 3'd2) ? 8'h24 :
                                (r == 3'd3) ? 8'h18 : (r == 3'd4) ? 8'h18 : (r == 3'd5) ? 8'h24 :
                                            (r == 3'd6) ? 8'h42 : 8'h81;  // 爆炸
                4'd13:
                    font_row = (r == 3'd0) ? 8'h3C : (r == 3'd1) ? 8'h66 : (r == 3'd2) ? 8'h06 :
                                (r == 3'd3) ? 8'h0C : (r == 3'd4) ? 8'h18 : (r == 3'd5) ? 8'h00 :
                                            (r == 3'd6) ? 8'h18 : 8'h00;  // 问号
                4'd14:
                    font_row = (r == 3'd3) ? 8'hFF : (r == 3'd4) ? 8'hFF : 8'h00;  // 横线
                4'd15:
                    font_row = 8'hFF;                                             // 实心
                default:
                    font_row = 8'h00;
            endcase
        end
    endfunction

    wire [7:0] frow = font_row(glyph, fy);
    wire       glyph_px = frow[3'd7 - fx];   // 1 = 画字模点

    // ---------------------------------------------------------------------------
    // 光标框（闪动）
    // ---------------------------------------------------------------------------
    reg [24:0] blink_q;
    always @(posedge clk or posedge reset) begin
        if (reset)
            blink_q <= 25'd0;
        else if (tick)
            blink_q <= blink_q + 25'd1;
    end
    wire blink = blink_q[24];

    wire cursor_here = (cursor_i[4:0] == ccol) && (cursor_i[12:8] == crow);
    wire on_border = (hx[3:0] == 4'd0) || (hx[3:0] == 4'd15) ||
         (vy[3:0] == 4'd0) || (vy[3:0] == 4'd15);
    wire cursor_box = cursor_here && blink && ctrl_i[0] && on_border;

    // ---------------------------------------------------------------------------
    // 颜色（3 位调色板 -> 4:4:4 RGB）
    // ---------------------------------------------------------------------------
    function [11:0] pal;
        input [2:0] c;
        begin
            case (c)
                3'd0:
                    pal = {4'h0, 4'h0, 4'h0};  // 黑
                3'd1:
                    pal = {4'h0, 4'h0, 4'hA};  // 深蓝
                3'd2:
                    pal = {4'h0, 4'hA, 4'h0};  // 绿
                3'd3:
                    pal = {4'h0, 4'hA, 4'hA};  // 青
                3'd4:
                    pal = {4'hA, 4'h0, 4'h0};  // 红
                3'd5:
                    pal = {4'hA, 4'h0, 4'hA};  // 洋红
                3'd6:
                    pal = {4'hA, 4'hA, 4'h0};  // 黄
                default:
                    pal = {4'hA, 4'hA, 4'hA};  // 浅灰
            endcase
        end
    endfunction

    wire [2:0] px_color = glyph_px ? gcolor : bgcolor;
    wire [2:0] px_final = cursor_box ? 3'd7 : px_color;
    wire [11:0] px_rgb = de ? pal(px_final) : 12'h000;

    always @(posedge clk or posedge reset) begin
        if (reset) begin
            {vga_r, vga_g, vga_b} <= 12'h000;
            vga_hs                <= 1'b1;
            vga_vs                <= 1'b1;
            frame_tick_o          <= 1'b0;
        end
        else if (tick) begin
            {vga_r, vga_g, vga_b} <= px_rgb;
            vga_hs                <= hs_n;
            vga_vs                <= vs_n;
            frame_tick_o          <= (hx == H_TOTAL - 1) && (vy == V_TOTAL - 1);
        end
    end

endmodule

`default_nettype wire
Tcl 一键重建