Atmel ATmega328P Xplained Mini MEGA328P-XMINI MEGA328P-XMINI Data Sheet
Product codes
MEGA328P-XMINI
12
ATmega48A/PA/88A/PA/168A/PA/328/P [DATASHEET]
Atmel-8271H-AVR- ATmega-Datasheet_08/2014
Two 8-bit output operands and one 8-bit result input
Two 8-bit output operands and one 16-bit result input
One 16-bit output operand and one 16-bit result input
shows the structure of the 32 general purpose working registers in the CPU.
Figure 7-2.
AVR
CPU General Purpose Working Registers
Most of the instructions operating on the Register File have direct access to all registers, and most of them are
single cycle instructions.
single cycle instructions.
As shown in
, 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 implemented as SRAM locations, this
memory organization provides great flexibility in access of the registers, as the X-, Y- and Z-pointer registers
can be set to index any register in the file.
memory organization provides great flexibility in access of the registers, as the X-, Y- and Z-pointer registers
can be set to index any register in the file.
7.4.1
The X-register, Y-register, and Z-register
The registers R26...R31 have some added functions to their general purpose usage. These registers are 16-bit
address pointers for indirect addressing of the data space. The three indirect address registers X, Y, and Z are
defined as described in
address pointers for indirect addressing of the data space. The three indirect address registers X, Y, and Z are
defined as described in
.
Figure 7-3.
The X-, Y-, and Z-registers
In the different addressing modes these address registers have functions as fixed displacement, automatic
increment, and automatic decrement (see the instruction set reference for details).
increment, and automatic decrement (see the instruction set reference for details).
7
0
Addr.
R0 0x00
R1
0x01
R2
0x02
…
R13
0x0D
General
R14
0x0E
Purpose
R15
0x0F
Working
R16
0x10
Registers
R17
0x11
…
R26
0x1A
X-register Low Byte
R27
0x1B
X-register High Byte
R28
0x1C
Y-register Low Byte
R29
0x1D
Y-register High Byte
R30
0x1E
Z-register Low Byte
R31
0x1F
Z-register High Byte
15
XH
XL
0
X-register
7
0
7
0
R27 (0x1B)
R26 (0x1A)
15
YH
YL
0
Y-register
7
0
7
0
R29 (0x1D)
R28 (0x1C)
15
ZH
ZL
0
Z-register
7
0
7
0
R31 (0x1F)
R30 (0x1E)