Manual

AT90S/LS8535

1041H–11/01

X-register, Y-register and Z-

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)