verilog基础问题

Tonyhai

-1=-32‘d1=32'hFFFFFFFF 麻烦解释下,谢谢啦!

Tonyhai

没人吗？

lam2

it's 2's complement

say +1 is 0000_0000_0000_0000_0000_0000_0000_0001 in binary
in 1's complement, then it's simply invert it:
1111_1111_1111_1111_1111_1111_1111_1110
But this kind of negative number has a problem, there're 2 zeros, namely 0 and ffff_ffff in hex.

Therefore, they've invent something called 2's complement.
it's 1's complement + 1, i.e.
-1 in 1's complement + 1, => 0xffff_fffe + 1 = 0xffff_ffff.

What's nice about 2's complement is e.g. 1 + -1 = 0x0000_0001 + 0xffff_ffff = 0!!!!

Tonyhai

thanks

lureny

补码，
但是这个是有符号数，也就是32位最多只能表示  -2^31 ~ (2^31-1)，注意，超过这个范围的就不要再和这个数做运算了，除非扩位

hawaii_e

先看看

yuanpin318

since int is 32 bit in verilog, -1 is express as complimentary code in verilog, that's why 32'hFFFFFFFF

shenhuijun

理解了~，谢谢

conggekui

不同進位的問題