Atmel AVR User Manual

2.2. Register Direct - Two Registers, Rd and Rr
Figure 2-2. Direct Register Addressing, Two Registers
Operands are contained in register r (Rr) and d (Rd). The result is stored in register d (Rd).
2.3. I/O Direct
Figure 2-3. I/O Direct Addressing
Operand address is contained in six bits of the instruction word. n is the destination or source register
address.
Note: Some complex AVR Microcontrollers have more peripheral units than can be supported within the
64 locations reserved in the opcode for I/O direct addressing. The extended I/O memory from address 64
to 255 can only be reached by data addressing, not I/O addressing.
Atmel AVR Instruction Set Manual [OTHER]
Atmel-0856L-AVR-Instruction-Set-Manual_Other-11/2016
15

Atmel AVR Specifications

General

Architecture	8-bit RISC
SRAM	Up to 16 KB
Clock Speed	Up to 20 MHz
Operating Voltage	1.8V to 5.5V
ADC	10-bit ADC
Communication Interfaces	SPI, I2C, USB
Packages	DIP, SOIC, QFN
Special Features	Watchdog Timer
Flash Memory	1KB to 256KB
EEPROM	64B to 4KB