"If" 在 always 块的敏感列表中的 always OR 条件内？

Question

这两个代码的行为是否相同？

always @(a == 1'b1) // I guess for this one, it's like a combinational if (AND gate logic : a AND 1).
    // code

和

always @(a) begin // I guess for this one, if a= 1 from the time 0,
                  // it won't go inside since there wouldn't be any change.
    if (a == 1) begin
    // code
    end
end

是真的吗？

这是一个基本问题，但我想知道我是否遗漏了什么，谢谢！

Answer 1

不，两者不一样。

Note that variables in the sensitivity list are considered as an event and hence they are not executed, rather just change in the variable is considered as a trigger to that event.

所以第一个总是阻塞

always @ (a==1'b1)

等同于：

always @ (a)

所以第一个总是块将执行同时a = 1和0，而在第二种情况下，因为"if"条件，所以只执行a = 1

"If" 在 always 块的敏感列表中的 always OR 条件内？

"If" inside an always OR condition in the sensitivity list of the always block?

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