at90ls4433 ATMEL Corporation, at90ls4433 Datasheet - Page 10

• Manufacturer Part Number: at90ls4433
• Description: At90s4433 8-bit Avr Microcontroller With 4k Bytes Of In-system Programmable Flash
• Manufacturer: ATMEL Corporation

General Purpose
Register File
X-register, Y-register and Z-
register
10
AT90S/LS4433
Figure 7 shows the structure of the 32 general purpose working registers in the CPU.
Figure 7. AVR CPU General Purpose Working Registers
All the register operating instructions in the instruction set have direct and single cycle
access to all registers. The only exceptions are 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 immediate 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 Figure 7, 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 phys-
ically implemented 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.
The registers R26..R31 have some added functions to their general purpose usage.
These registers are address pointers for indirect addressing of the Data Space. The
three indirect address registers X, Y, and Z are defined as:
Figure 8. X-, Y-, and Z-registers
X - register
Y - register
Z - register
Registers
Purpose
Working
General
15
7
15
7
15
7
R29 ($1D)
R27 ($1B)
R31 ($1F)
7
R13
R14
R15
R16
R17
R26
R27
R28
R29
R30
R31
R0
R1
R2
…
…
0
0
0
0
7
7
7
Addr.
$0D
$1C
$1D
$00
$01
$02
$0E
$0F
$10
$11
$1A
$1B
$1E
$1F
R28 ($1C)
R26 ($1A)
R30 ($1E)
X-register High Byte
Y-register High Byte
Z-register High Byte
X-register Low Byte
Y-register Low Byte
Z-register Low Byte
1042H–AVR–04/03
0
0
0
0
0
0