ATMEGA128A DATASHEET PDF

The device operates between 2. By executing powerful instructions in a single clock cycle, the device achieves throughputs approaching 1 MIPS per MHz, balancing power consumption and processing speed. IAR offers a completely integrated development environment incorporating a compiler, an assembler, a linker and a debugger. Finding the right compiler to support your device is simple:.

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All the 32 registers are directly connected to the Arithmetic Logic Unit ALU , allowing two independentregisters to be accessed in one single instruction executed in one clock cycle. Theresulting architecture is more code efficient while achieving throughputs up to ten times fasterthan conventional CISC microcontrollers.

The Power-down mode saves the register contents but freezes the Oscillator, disabling allother chip functions until the next interrupt or Hardware Reset. In Power-save mode, the asynchronoustimer continues to run, allowing the user to maintain a timer base while the rest of thedevice is sleeping. Thisallows very fast start-up combined with low power consumption.

The boot program can use any interface to download the applicationprogram in the application Flash memory. Software in the Boot Flash section will continue to runwhile the Application Flash section is updated, providing true Read-While-Write operation.

Also, theincreased number of interrupt vectors might be a problem if the code uses absolute addresses. To solve these problems, an ATmega compatibility mode can be selected by programmingthe fuse MC.

Also, the Extended Interrupt vectors are removed. However, some new featuresin ATmegaA are not available in this compatibility mode, these features are listedbelow Only the eight least significant bits ofthe Baud Rate Register is available. ThePort A output buffers have symmetrical drive characteristics with both high sink and sourcecapability. As inputs, Port A pins that are externally pulled low will source current if the pull-upresistors are activated.

The Port A pins are tri-stated when a reset condition becomes active,even if the clock is not running. ThePort B output buffers have symmetrical drive characteristics with both high sink and sourcecapability. As inputs, Port B pins that are externally pulled low will source current if the pull-upresistors are activated.

The Port B pins are tri-stated when a reset condition becomes active,even if the clock is not running. Port B also serves the functions of various special features of the ATmegaA as listed onpage ThePort C output buffers have symmetrical drive characteristics with both high sink and sourcecapability.

As inputs, Port C pins that are externally pulled low will source current if the pull-upresistors are activated. The Port C pins are tri-stated when a reset condition becomes active,even if the clock is not running. Port C also serves the functions of special features of the ATmegaA as listed on page InATmega compatibility mode, Port C is output only, and the port C pins are not tri-statedwhen a reset condition becomes active. ThePort D output buffers have symmetrical drive characteristics with both high sink and sourcecapability.

As inputs, Port D pins that are externally pulled low will source current if the pull-upresistors are activated. The Port D pins are tri-stated when a reset condition becomes active,even if the clock is not running. Port D also serves the functions of various special features of the ATmegaA as listed onpage ThePort E output buffers have symmetrical drive characteristics with both high sink and sourcecapability. As inputs, Port E pins that are externally pulled low will source current if the pull-upresistors are activated.

The Port E pins are tri-stated when a reset condition becomes active,even if the clock is not running. Port E also serves the functions of various special features of the ATmegaA as listed onpage Port pinscan provide internal pull-up resistors selected for each bit.

ATmegaA metrical drive characteristics with both high sink and source capability. As inputs, Port F pinsthat are externally pulled low will source current if the pull-up resistors are activated. The Port Fpins are tri-stated when a reset condition becomes active, even if the clock is not running. ThePort G output buffers have symmetrical drive characteristics with both high sink and sourcecapability. As inputs, Port G pins that are externally pulled low will source current if the pull-upresistors are activated.

The Port G pins are tri-stated when a reset condition becomes active,even if the clock is not running. Port G also serves the functions of various special features. The port G pins are tri-stated when a reset condition becomes active, even if the clock is notrunning. PG3 and PG4 are oscillator pins.

A low level on this pin for longer than the minimum pulse length will generate areset, even if the clock is not running. Shorter pulses are not guaranteed to generate a reset. Input to the inverting Oscillator amplifier and input to the internal clock operating circuit.

Output from the inverting Oscillator amplifier. PEN has no function during normal operation. ATmegaA 3. Note: 1. Data Retention5. This datasheet contains simple code examples that briefly show how to use various parts of thedevice. These code examples assume that the part specific header file is included before compilation.

Be aware that not all C compiler vendors include bit definitions in the header files andinterrupt handling in C is compiler dependent. Please confirm with the C compiler documentationfor more details. ATmegaA 6. The main function of theCPU core is to ensure correct program execution.

The CPU must therefore be able to accessmemories, perform calculations, control peripherals and handle interrupts. Instructions in the program memory areexecuted with a single level pipelining. While one instruction is being executed, the next instructionis pre-fetched from the program memory.

This concept enables instructions to be executedin every clock cycle. The program memory is In-System Reprogrammable Flash memory. In a typicalALU operation, two operands are output from the Register file, the operation is executed,and the result is stored back in the Register file — in one clock cycle. Six of the 32 registers can be used as three bit indirect address register pointers for DataSpace addressing — enabling efficient address calculations.

ATmegaA can also be used as an address pointer for look up tables in Flash Program memory. Theseadded function registers are the bit X-register, Y-register and Z-register, described later inthis section. The ALU supports arithmetic and logic operations between registers or between a constant anda register. Single register operations can also be executed in the ALU.

After an arithmetic operation,the Status Register is updated to reflect information about the result of the operation. Program flow is provided by conditional and unconditional jump and call instructions, able todirectly address the whole address space.

Most AVR instructions have a single bit word format. Every program memory address contains a bit or bit instruction. Program Flash memory space is divided in two sections, the Boot Program section and theApplication Program section. All user programs mustinitialize the SP in the reset routine before subroutines or interrupts are executed. The memory spaces in the AVR architecture are all linear and regular memory maps.

All interrupts have a separate interrupt vector in theinterrupt vector table. The interrupts have priority in accordance with their interrupt vector position. The lower the interrupt vector address, the higher the priority. Within a single clock cycle, arithmetic operations between general purposeregisters or between a register and an immediate are executed.

The ALU operations are dividedinto three main categories — arithmetic, logical, and bit-functions. This information can be used for altering program flow in order to performconditional operations. This will in many cases remove the need for using thededicated compare instructions, resulting in faster and more compact code. The status register is not automatically stored when entering an interrupt routine and restoredwhen returning from an interrupt.

This must be handled by software. The individual interruptenable control is then performed in separate control registers. If the Global Interrupt EnableRegister is cleared, none of the interrupts are enabled independent of the individual interruptenable settings. The I-bit is cleared by hardware after an interrupt has occurred, and is set bythe RETI instruction to enable subsequent interrupts.

Half carry is useful inBCD arithmetic. Figure As shown in Figure , each register is also assigned a data memory address, mapping themdirectly into the first 32 locations of the user Data Space.

Although not being physically implementedas SRAM locations, this memory organization provides great flexibility in access of theregisters, as the X-, Y-, and Z-pointer Registers can be set to index any register in the file. These registersare bit address pointers for indirect addressing of the Data Space. The three indirectaddress registers X, Y, and Z are described in Figure ATmegaA Figure The Stack is mainly used for storing temporary data, for storing local variables and for storingreturn addresses after interrupts and subroutine calls.

Note that the Stack is implemented asgrowing from higher to lower memory locations. The Stack Pointer Register always points to thetop of the Stack. The Stack in the data SRAM must be defined by the program before any subroutine calls areexecuted or interrupts are enabled. See Table for Stack Pointer details. Table

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