什么FUNC在R-格式的指令来设定？ [英] What does func means in R-Format instruction set?

问题描述

我很新的汇编语言即可。我正在读关于 MIPS 架构和我坚持在注册格式（R-格式）的最后一个字段。下面是它的视觉重新presentation，

任何人都可以请帮我出的什么是第六场手段并如何计算呢？
先谢谢了。

I am very new to Assembly language. I was reading about MIPS architecture and I am stuck with the last field of the Register Format (R-Format). Here is its visual representation, Can anyone please help me out with what does the sixth field means and how do we calculate it? Thanks in advance.

推荐答案

由于说明提及的所有R型的指令（如添加，键， ， SLL 等）必须设置为0 6最显著位（= OP），这意味着他们是为了区别开来的唯一途径看6至少显著位（= FUNCT）。换句话说，他们确定的指令类型。也许一个例子帮助。

As the description mentions all R-type instructions (e.g. ADD, AND, SLL and others) have the 6 most significant bits (= op) set to 0, that means the only way to distinguish between them is to look at the 6 least significant bits (= funct). In other words they determine the the instruction type. Perhaps an example will help.

ADD $1, $2, $3 

有：

op = 0 (as all R-type instructions)
rs = 2
rt = 3
rd = 1
shamt = 0
funct = 0x20 = 0b00000100000 = 32

编码将因此是：

0000 0000 0100 0011 0000 1000 0010 0000

有关如 XOR （另一种R型）指令FUNCT是 0b100110 = 0×26 = 38 。所以，你通过查找你要带code什么指令计算了。

For e.g. XOR (another R-type) instruction funct is 0b100110 = 0x26 = 38. So you "calculate" it by looking up what instruction you want to encode.

（从 MIPS指令参考拍摄）。

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