为什么我选择的信号分配不起作用? [英] Why does my selected signal assignment not work?

问题描述

我在 VHDL 代码中选择的信号分配有什么问题?

What did I do wrong with the selected signal assignment in my VHDL code?

with s select x <= a when (s = '1')
         else y <= a when (s = '0');

我也试过这个:

with s select x <= a when '1';
with s select y <= a when '0';

推荐答案

您想做什么并不完全清楚.从您向我们展示的内容来看，在我看来，您想创建一个由信号 s(1 个输入，2 个输出)控制的解复用器，其中 x <= a when s='1' 和 y <= a when s='0'

It's not completly clear what you want to do. From what you showed us, it seems to me that you want to create a demux controlled by signal s (1 input, 2 outputs), where x <= a when s='1' and y <= a when s='0'

在您想要创建多路复用器(n 个输入，1 个输出)的情况​​下，应该使用 select.也就是说，与解复用器相反！

The use of select should be done in cases when you want to create a mux (n inputs, 1 output). That is, the opposite of a demux!

我建议您使用简单的 if 语句来创建多路分配器.

I would recommend you to use a simple if statement to create a demux.

示例:

if s='1' then x <= a;否则 y <= a;结束如果;

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