7
ATtiny22/22L
X-Register, Y-Register, and Z-Register
The registers R26..R31 have some added functions to their general purpose usage. These registers are the address point-
ers for indirect addressing of the Data Space. The three indirect address registers X, Y and Z are defined as:
Figure 6. The X, Y, and Z Registers
In the different addressing modes these address registers have functions as fixed displacement, automatic increment and
decrement (see the descriptions for the different instructions).
ALU - Arithmetic Logic Unit
The high-performance AVR ALU operates in direct connection with all the 32 general purpose working registers. Within a
single clock cycle, ALU operations between registers in the register file are executed. The ALU operations are divided into
three main categories - arithmetic, logic and bit-functions
In-System Programmable Flash Program Memory
The ATtiny22/L contains 2K bytes on-chip In-System Programmable Flash memory for program storage. Since all instruc-
tions are 16- or 32-bit words, the Flash is organized as 1K x 16. The Flash memory has an endurance of at least 1000
write/erase cycles.
The ATtiny22/L Program Counter PC is 10 bits wide, hence addressing the 1024 program memory addresses. See
page 38 for a detailed description on Flash data programming.
Constant tables must be allocated within the address 0-2K (see the LPM - Load Program Memory instruction description).
See page 9 for the different addressing modes.
EEPROM Data Memory
The ATtiny22/L contains 128 bytes of EEPROM data memory. It is organized as a separate data space, in which single
bytes can be read and written. The EEPROM has an endurance of at least 100,000 write/erase cycles. The access
between the EEPROM and the CPU is described on page 30 specifying the EEPROM address register, the EEPROM data
register, and the EEPROM control register.
For the SPI data downloading, see page 38 for a detailed description.
15
0
X - register
7
0
7
0
R27 ($1B)
R26 ($1A)
15
0
Y - register
7
0
7
0
R29 ($1D)
R28 ($1C)
15
0
Z - register
7
0
7
0
R31 ($1F)
R30 ($1E)
