AT43USB326 datasheet(8/102 Pages) ATMEL

8 / 102 page

AT43USB326

3313D–USB–04/06

immediate constant data. These instructions apply to the second half of the registers in the

between two registers or on a single register apply to the entire register file.

As shown in Table 1, each register is also assigned a data memory address, mapping them

directly into the first 32 locations of the user Data Space. Although not being physically imple-

mented as SRAM locations, this memory organization provides great flexibility in access of the

registers, as the X-, Y-, and Z-registers can be set to index any register in the file.

X-, Y- and Z-

Registers

Registers R26..R31 contain some added functions to their general-purpose usage. These reg-

isters are address pointers for indirect addressing of the Data Space. The three indirect

address registers X, Y, and Z are defined as:

In the different addressing modes these address registers have functions as fixed displace-

ment, 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 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, log-

ical and bit-functions.

Program Memory

The AT43USB326 contains 16K bytes on-chip masked programmable ROM. Since all instruc-

tions are 16- or 32-bit words, the program memory is organized as 8K x 16. The AT43USB326

Program Counter (PC) is 13 bits wide, thus addressing the 8,192 program memory addresses.

Constant tables can be allocated within the entire program memory address space (see the

LPM - Load Program Memory instruction description).

X-register

R27 ($1B)

R26 ($1A)

Y-register

R29 ($1D)

R28 ($1C)

Z-register

R30 ($1F)

R31 ($1E)

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