位操作 - 仅改变最后4位

Question

I want to set the last 4 bits of an int to another int.

So for example you have this int: 1100 0001 . And I only want to change the last four bits with another int for example: 0000 0110 . All the other bits should remain unchanged and it has to be in one statement (I'm sorry for my horrible explanation).

The folowing statement does work, but it seems bad practice and It would only work with an uint8_t

unint8_t count = 6; //0000 0110
PORTC = ((PORTC >> 4) << 4) | count; //PORTC = 1100

The outcome of PORTC is 1100 0110 and this is what I want, however I want it to work with any integer. What is another (better) way of doing this?

NOTE: It must be one statement.

Answer 1

您首先要使用掩码设置AND目标号码，该掩码除了设置4个最低位以外，然后使用与第一个数字的最低4位的OR。

PORTC = (PORTC & ~0xfULL) | ( count & 0xf );