花括号在Verilog中是什么意思？ [英] What do curly braces mean in Verilog?

问题描述

我很难理解Verilog中的以下语法：

I am having a hard time understanding the following syntax in Verilog:

input  [15:0] a;      // 16-bit input
output [31:0] result; // 32-bit output
assign result = {{16{a[15]}}, {a[15:0]}};

我知道 assign 语句会进行连接直到使用导线和组合逻辑的 result 总线，但是花括号和 16 {a [15]} ？

I know the assign statement will wire something up to the result bus using wires and combinational logic, but what's up with the curly braces and 16{a[15]}?

推荐答案

花括号表示从左上的最高有效位（MSB）到最低有效的位的级联（LSB）在右边。您正在创建一个32位总线（结果），该总线的16个最高有效位由一个总线的第15位（MSB）的16个副本组成，并且其16个最低有效位仅由一个总线组成（这种特殊的结构是已知的为符号扩展，例如需要将负数右移 two'scomplement 形式的数字，并保持负数而不是引入

The curly braces mean concatenation, from most significant bit (MSB) on the left down to the least significant bit (LSB) on the right. You are creating a 32-bit bus (result) whose 16 most significant bits consist of 16 copies of bit 15 (the MSB) of the a bus, and whose 16 least significant bits consist of just the a bus (this particular construction is known as sign extension, which is needed e.g. to right-shift a negative number in two's complement form and keep it negative rather than introduce zeros into the MSBits).

有一个教程此处 *，但仅比上一段解释得更多。

There is a tutorial here*, but it doesn't explain too much more than the above paragraph.

对于它的价值而言， a [15：0] 周围的嵌套花括号是多余的。

For what it's worth, the nested curly braces around a[15:0] are superfluous.

*请注意：当演示多个串联时，教程链接中的示例包含错字-（2 {C}} 应该成为 {2 {2}} 。

*Beware: the example within the tutorial link contains a typo when demonstrating multiple concatenations - the (2{C}} should be a {2{2}}.

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