Rainbow Electronics AT86RF401 - Manual (Page 20)

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AT86RF401
1424D–RKE–09/02
The X, Y and Z Registers 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 shown in Figure 9.
Figure 9. The X, Y and Z Registers
In the different addressing modes, these address registers have functions as fixed dis-
placement, automatic increment and decrement (see the descriptions for the different
instructions).
Arithmetic Logic Unit
(ALU) The high-performance AVR ALU operates in direct connection with all the 32 general-
purpose working registers. Within a single clock cycle, ALU operations between regis-
ters in the register file are executed. The ALU operations are divided into three main
categories: arithmetic, logical and bit-functions. The multiplier is not present in this ver-
sion of the core. Therefore, the MUL instruction is not supported.
In-system Self-
programmable Flash
Program Memory The AT86RF401 contains 2 Kbytes of on-chip Flash memory for program storage. Since
all instructions are 16- or 32-bit words, the Flash is organized as 1K x 16.
The Flash memory has an endurance of at least 1000 write/erase cycles. The PC is 10
bits wide, thus addressing the 1024 program memory locations. See the Memory Pro-
gramming section (page 13) for a detailed description on Flash data serial downloading.
Constant tables can be allocated within the entire program memory address space (see
Table 10, Instruction Set, page 44).
15 XH XL 0
X Register 70 0 7 0
R27 ($1B) R26 ($1A)
15 YH YL 0
Y Register 70 0 7 0
R29 ($1D) R28 ($1C)
15 ZH ZL 0
Z Register 70 0 7 0
R30 ($1F) R31 ($1E)