Registers

Registers are a key element of AVR microcontrollers. There are various types of registers, including general-purpose, special-purpose, and status registers. General-purpose registers are used to store temporary data. Special registers control microcontroller functions, such as timers or ADC. Status registers store information about the processor state, such as carry or zero flags. Each register has a specific function and is accessible through particular assembler instructions. Registers allow quick access to data and control over the processor.

AVR CPU General Purpose Working Registers (R0-R31)

R0-R15: Basic general-purpose registers used for various arithmetic and logical operations.

R16-R31: General-purpose registers that can be used with immediate

The X-register, Y-register, and Z-register: address pointers for indirect addressing R26-R31: These registers have additional functions as 16-bit address pointers for indirectly addressing the data space. They are defined as X, Y, and Z registers.

Other registers:

RAMPX, RAMPY, RAMPZ: Registers concatenated with the X-, Y-, and Z-registers, enabling indirect addressing of the entire data space on MCUs with more than 64 KB of data space, and constant data fetch on MCUs with more than 64 KB of program space.

RAMPD: Register concatenated with the Z-register, enabling direct addressing of the whole data space on MCUs with more than 64 KB data space.

EIND: Register concatenated with the Z-register, enabling indirect jump and call to the entire program space on MCUs with more than 64K words (128 KB) of program space.