XMEGAD datasheet(7/309 Pages) ATMEL

7 / 309 page

8210B–AVR–04/10

XMEGA D

The Program Memory is divided in two sections, the Application Program section and the Boot

Program section. Both sections have dedicated Lock bits for write and read/write protection. The

SPM instruction that is used for self-programming of the Application Flash memory must reside

in the Boot Program section. A third section exists inside the Application section. This section,

the Application Table section, has separate Lock bits for write and read/write protection. The

Application Table section can be used for storing non-volatile data or application software.

3.4

ALU - Arithmetic Logic Unit

The Arithmetic Logic Unit (ALU) supports arithmetic and logic operations between registers or

between a constant and a register. Single register operations can also be executed. The ALU

operates in direct connection with all the 32 general purpose registers. In a typical single cycle

ALU operation, two operands are output from the Register File, the operation is executed, and

the result is stored back in the Register File.

In order to operate on data in the Data Memory, these must first be loaded into the Register File.

After the operation, the data can be stored from the Register File and back to the Data Memory.

The ALU operations are divided into three main categories - arithmetic, logical, and bit-functions.

After an arithmetic or logic operation, the Status Register is updated to reflect information about

the result of the operation.

3.4.1

Hardware Multiplier

The multiplier is capable of multiplying two 8-bit numbers into a 16-bit result. The hardware mul-

tiplier supports different variations of signed and unsigned integer and fractional numbers:

• Multiplication of unsigned integers.

• Multiplication of signed integers.

• Multiplication of a signed integer with an unsigned integer.

• Multiplication of unsigned fractional numbers.

• Multiplication of signed fractional numbers.

• Multiplication of a signed fractional number and with an unsigned.

A multiplication takes two CPU clock cycles.

3.5

Program Flow

After reset, the program will start to execute from program address 0. Program flow is provided

by conditional and unconditional jump and call instructions, able to directly address the whole

address space. Most instructions have a single 16-bit word format. Every program memory

address contains a 16- or 32-bit instruction. The Program Counter (PC) addresses the location

from where instructions are fetched. During interrupts and subroutine calls, the return address

PC is stored on the Stack.

When an enabled interrupt occurs, the Program Counter is vectored to the actual interrupt vector

in order to execute the interrupt handling routine. Hardware clears the corresponding interrupt

flag automatically.

XMEGAD Datasheet(PDF) 7 Page - ATMEL Corporation

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