Rainbow Electronics AT90LS8535 - Manual (Page 10)

10
AT90S/LS8535
1041H–11/01
X-register, Y-register and Z-
register 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 in Figure 7.
Figure 7. X-, Y-, and Z-register
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).
ALU – Arithmetic Logic
Unit 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.
In-System Programmable
Flash Program Memory The AT90S8535 contains 8K bytes On-chip, In-System Programmable Flash memory
for program storage. Since all instructions are 16- or 32-bit words, the Flash is orga-
nized as 4K x 16. The Flash memory has an endurance of at least 1000 write/erase
cycles. The AT90S8535 Program Counter (PC) is 12 bits wide, thus addressing the
4096 program memory addresses.
See page 99 for a detailed description on Flash data downloading.
See page 12 for the different program memory addressing modes.
15 0
X-register 7 0 7 0
R27 ($1B) R26 ($1A)
15 0
Y-register 7 0 7 0
R29 ($1D) R28 ($1C)
15 0
Z-register 7 0 7 0
R31 ($1F) R30 ($1E)