AT43USB325 datasheet(9/109 Pages) ATMEL

9 / 109 page

3355C–USB–4/05

AT43USB325

General-purpose Register File

All register operating instructions in the instruction set have direct and single cycle access to all

registers. The only exception is the five constant arithmetic and logic instructions SBCI, SUBI,

CPI, ANDI, and ORI between a constant and a register, and the LDI instruction for load immedi-

ate constant data. These instructions apply to the second half of the registers in the register file

– R16..R31. The general SBC, SUB, CP, AND, and OR and all other operations between two

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

As shown in Table 3-1, 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.

Table 3-1.

AVR CPU General-purpose Working Register

Address

Comment

$00

$01

$02

R13

$0D

R14

$0E

R15

$0F

R16

$10

R17

$11

R26

$1A

X-register low byte

R27

$1B

X-register high byte

R28

$1C

Y-register low byte

R29

$1D

Y-register high byte

R30

$1E

Z-register low byte

R31

$1F

Z-register high byte

AT43USB325 Datasheet(PDF) 9 Page - ATMEL Corporation

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