at90ls8535-8mi ATMEL Corporation, at90ls8535-8mi Datasheet - Page 8

• Manufacturer Part Number: at90ls8535-8mi
• Description: 8-bit Microcontroller With 8k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

8
AT90S/LS8535
assigned the 32 lowermost Data Space addresses ($00 - $1F), allowing them to be
accessed as though they were ordinary memory locations.
The I/O memory space contains 64 addresses for CPU peripheral functions as Control
Registers, Timer/Counters, A/D converters and other I/O functions. The I/O memory can
be accessed directly or as the Data Space locations following those of the register file,
$20 - $5F.
The AVR uses a Harvard architecture concept – with separate memories and buses for
program and data. The program memory is executed with a two-stage pipeline. While
one instruction is being executed, the next instruction is pre-fetched from the program
memory. This concept enables instructions to be executed in every clock cycle. The pro-
gram memory is in-system downloadable Flash memory.
With the relative jump and call instructions, the whole 4K address space is directly
accessed. Most AVR instructions have a single 16-bit word format. Every program
memory address contains a 16- or 32-bit instruction.
During interrupts and subroutine calls, the return address Program Counter (PC) is
stored on the stack. The stack is effectively allocated in the general data SRAM and
consequently, the stack size is only limited by the total SRAM size and the usage of the
SRAM. All user programs must initialize the SP in the reset routine (before subroutines
or interrupts are executed). The 10-bit stack pointer (SP) is read/write-accessible in the
I/O space.
The 512 bytes data SRAM can be easily accessed through the five different addressing
modes supported in the AVR architecture.
The memory spaces in the AVR architecture are all linear and regular memory maps.
Figure 5. Memory Maps
A flexible interrupt module has its control registers in the I/O space with an additional
global interrupt enable bit in the status register. All the different interrupts have a sepa-
rate interrupt vector in the interrupt vector table at the beginning of the program
Program Memory
Program Flash
(4K x 16)
$000
$FFF
Working Registers
32 Gen. Purpose
64 I/O Registers
Internal SRAM
Data Memory
(512 x 8)
$025F
$0000
$001F
$0020
$005F
$0060
Data Memory
EEPROM
(512 x 8)
1041H–11/01
$000
$1FF