AVR shift algorithm detailed explanation

Many beginners are confused by the shift algorithm, which is in the form of (1<AVR's USART.

UCSRC = (1<

UCSR0B = (1<// RXCIE=1;TXCIE=1;UDREIE=0;RXEN=1;TXEN= 1

This way of writing is a blessing for experts, because these codes explain which bits of the register are operated on, and the meaning of its operation can be seen; but it is a curse for novices, because novices cannot understand such programs.

Let's go back to the beginning and explain what the shift algorithm is:

For example: A = (1<<2), 1 written in binary is 0000 0001, and this 1 shifted left 2 bits is 0000 0100, so the resulting number A is 0000 0100, which is 0x04.

For example: B = (2<<4), 2 is written as 0000 0010 in binary, and this number shifted left 4 bits is 0010 0000, so the resulting number B is 0010 0000, which is 0x20.

Both of the above shift algorithms are correct. The first way of writing it represents a number with the third digit being 1 and the rest being 0s, and the numbering starts from 0. For example, (1<<0) represents 0000 0001, and (1<<7) represents 1000 0000. However, the second way of writing it does not have this meaning. Shifting is also used for multiplication and division. Shifting left by one bit multiplies by 2, and shifting right by one bit divides by 2. The number obtained by shifting 2 left by four bits in the second way of writing it above is 2×2×2×2×2=32, which is 0x20 above.

Let’s look at the above sentence again: UCSRC = (1<

UCSRC is an eight-bit register related to serial port communication. Each bit of it has a special definition. We can see the following by checking the data sheet.

The header file iom16v.h and similar files included in the program will have a definition like #define URSEL 7. 1<