AT90S2313
8
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
pointers for indirect addressing of the Data Space. The three indirect address registers X, Y and Z are defined as:
Figure 7. 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, logical and bit-functions.
In-System Programmable Flash Program Memory
The AT90S2313 contains 2K bytes on-chip In-System Programmable Flash memory for program storage. Since all
instructions 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 AT90S2313 Program Counter PC is 10 bits wide, thus addressing the 1024 program memory addresses.
See page 57 for a detailed description on Flash data downloading. See page 10 for the different addressing modes.
EEPROM Data Memory
The AT90S2313 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 38 specifying the EEPROM address register, the EEPROM data
register, and the EEPROM control register.
For the SPI data downloading, see page 65 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)
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