Suppose you're building a circuit to process scancodes from a PS/2 keyboard for a game. Given the last two bytes of scancodes received, you need to indicate whether one of the arrow keys on the keyboard have been pressed. This involves a fairly simple mapping, which can be implemented as a case statement (or if-elseif) with four cases. 假设你正在为一款游戏构建一个电路，用于处理来自 PS/2 键盘的扫描码。已知接收到的扫描码的最后两个字节，你需要判断键盘上的某个方向键是否被按下。这涉及一个相当简单的映射，可通过一个包含四种情况的 case 语句（或 if-elseif 语句）来实现
Your circuit has one 16-bit input, and four outputs. Build this circuit that recognizes these four scancodes and asserts the correct output. 你的电路有一个16位输入和四个输出。构建一个能够识别这四个扫描码并输出对应正确信号的电路。
To avoid creating latches, all outputs must be assigned a value in all possible conditions (See also always_if2). Simply having a default case is not enough. You must assign a value to all four outputs in all four cases and the default case. This can involve a lot of unnecessary typing. One easy way around this is to assign a "default value" to the outputs before the case statement: 为了避免产生锁存器，所有输出在所有可能的条件下都必须被赋值（另见 always_if2）。仅设置一个默认情况是不够的。你必须在全部四种情况和默认情况中为所有四个输出赋值。这可能需要大量不必要的输入。一个简单的解决方法是在 case 语句之前为输出分配一个“默认值”：
This style of code ensures the outputs are assigned a value (of 0) in all possible cases unless the case statement overrides the assignment. This also means that a default: case item becomes unnecessary. 这种代码风格确保在所有可能的情况下，输出都会被赋值为 0，除非 case 语句覆盖了该赋值。这也意味着 default: 分支项变得没有必要。
Reminder: The logic synthesizer generates a combinational circuit that behaves equivalently to what the code describes. Hardware does not "execute" the lines of code in sequence. 提醒：逻辑综合器会生成一个与代码描述行为等效的组合电路。硬件不会按顺序“执行”代码行。
Module Declaration
Write your solution here
Solution
module top_module (
input [15:0] scancode,
output reg left,
output reg down,
output reg right,
output reg up
);
always @(*) begin
up = 1'b0;
down = 1'b0;
left = 1'b0;
right = 1'b0;
case (scancode)
16'he06b : left = 1'b1;
16'he072 : down = 1'b1;
16'he074 : right = 1'b1;
16'he075 : up = 1'b1;
endcase
end
endmodule贡献者
dz13718198068