Datasheet

11
XMEGA B [DATASHEET]
8291B–AVR–01/2013
Figure 3-4. AVR CPU general purpose working registers.
The register file is located in a separate address space, and so the registers are not accessible as data memory.
3.9.1 The X-, Y-, and Z- Registers
Registers R26..R31 have added functions besides their general-purpose usage.
These registers can form 16-bit address pointers for addressing data memory. These three address registers are called
the X-register, Y-register, and Z-register. The Z-register can also be used as an address pointer to read from and/or write
to the flash program memory, signature rows, fuses, and lock bits.
Figure 3-5. The X-, Y- and Z-registers.
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
Bit (individually) 7 R27 0 7 R26 0
X-register XH XL
Bit (X-register) 15 8 7 0
Bit (individually) 7 R29 0 7 R28 0
Y-register YH YL
Bit (Y-register) 15 8 7 0
Bit (individually) 7 R31 0 7 R30 0
Z-register ZH ZL
Bit (Z-register) 15 8 7 0