b200: import original Kintex-7 clone port

top/b200/pps_switch.v

@@ -0,0 +1,72 @@
+`timescale 1ns / 1ps
+
+// pps_switch.v
+module pps_switch (
+    input  wire        clk,          // 系统时钟（≥10 MHz 推荐）
+    input  wire        rst_n,        // 低电平有效异步复位
+    input  wire        gps_pps,      // GPS_PPS 输入
+    input  wire        ext_pps,      // EXT_PPS 输入
+    output reg         pps_out       // 最终输出的PPS脉冲
+);
+
+    // 跟踪当前激活的PPS源
+    reg active_pps_source;  // 0=GPS, 1=EXT
+    
+    // 边沿检测：上升沿产生一个时钟周期的高脉冲
+    wire gps_posedge;
+    wire ext_posedge;
+
+    edge_detect u_gps_edge (
+        .clk(clk),
+        .rst_n(rst_n),
+        .din(gps_pps),
+        .dout(gps_posedge)
+    );
+
+    edge_detect u_ext_edge (
+        .clk(clk),
+        .rst_n(rst_n),
+        .din(ext_pps),
+        .dout(ext_posedge)
+    );
+
+    // 状态机：0=等待GPS，1=等待EXT
+    reg [1:0] state;
+    localparam S_GPS = 2'b00;
+    localparam S_EXT = 2'b01;
+
+    always @(posedge clk or negedge rst_n) begin
+        if (!rst_n) begin
+            state   <= S_GPS;
+            active_pps_source <= 1'b0;  // 默认GPS
+        end 
+        else begin
+            case (state)
+                S_GPS: begin
+                    if (gps_posedge) begin
+                        state   <= S_GPS; // 保持GPS优先
+                        active_pps_source <= 1'b0;  // 激活GPS
+                    end else if (ext_posedge) begin
+                        state   <= S_GPS; // 仍保持GPS优先，但允许EXT临时补位
+                        active_pps_source <= 1'b1;  // 激活EXT
+                    end
+                end
+                default: begin  // 简化处理，实际应用中可扩展状态机
+                    if (ext_posedge) begin
+                        state   <= S_GPS; // 回到GPS等待
+                        active_pps_source <= 1'b1;  // 激活EXT
+                    end
+                end
+            endcase
+        end
+    end
+
+    // 输出逻辑
+    always @(posedge clk or negedge rst_n) begin
+        if (!rst_n)
+            pps_out <= 1'b0;
+        else 
+            pps_out <= active_pps_source ? ext_pps : gps_pps;
+    end
+
+endmodule