AVR I/O memory operations

All I/O registers can be accessed through the IN (I/O port input) and OUT (output to I/O port) instructions. These instructions are used to transfer and exchange data between the 32 general registers and the I/O register space, and the instruction cycle is 1 clock cycle. In addition, the registers (the first 32) with an address range of $00-$1F can also be used to implement bit operations and bit judgment jumps. The SBI (specified position in the I/O register is set to 1) and CBI (specified bit in the I/O register is cleared to zero) instructions can directly perform bit operations on each bit in the I/O register. Using the SBIS (jump if the specified bit in the I/O register is 1) and SBIC (jump if the specified bit in the I/O register is 0) instructions can verify and judge the values ​​of each bit in these I/O registers, and implement a jump to skip an instruction and execute the next instruction.

I/O register addresses $OO to $3F are used in the I/O register-specific instructions IN, OUT, SBI, CBI, SBIS, and SBIC.

When addressing an I/O register in SRAM mode, you must add $0020 to its address to map it to the address in the data memory space. In this book, I/O register addresses are given in two address representations: the I/O register space address and the mapped address in the data memory space (in parentheses).

Replenish:

All I/O and peripherals of the ATmega128 are placed in the I/O space. All I/O locations can be accessed through the IN and OUT instructions, which transfer data between the 32 general working registers and the I/O. The I/O registers have addresses from 0x00 to 0x1F. You can also use the SBI and CBI instructions to directly address a bit, while SBIS and SBIC are used to check the value of a specific bit. For more information, see the instruction set. When using the IN and OUT instructions, the address must be between 0x00 and 0x3F. If you want to access the I/O registers through the LD and ST instructions like SRAM, add 0x20 to the corresponding address.