8/16-bit Atmel XMEGA Microcontroller
ATxmega128A4U, ATxmega64A4U*,
ATxmega32A4U, ATxmega16A4U
*Preliminary
Features
z High-performance, low-power Atmel® AVR® XMEGA® 8/16-bit Microcontroller
z Nonvolatile program and data memories
z 16K - 128KB of in-system self-programmable flash
z 4K - 8KB boot section
z 1K - 2KB EEPROM
z 2K - 8KB internal SRAM
z Peripheral Features
z Four-channel DMA controller
z Eight-channel event system
z Five 16-bit timer/counters
z Three timer/counters with 4 output compare or input capture channels
z Two timer/counters with 2 output compare or input capture channels
z High-resolution extensions on all timer/counters
z Advanced waveform extension (AWeX) on one timer/counter
z One USB device interface
z USB 2.0 full speed (12Mbps) and low speed (1.5Mbps) device compliant
z 32 Endpoints with full configuration flexibility
z Five USARTs with IrDA support for one USART
z Two Two-wire interfaces with dual address match (I
z Two serial peripheral interfaces (SPIs)
z AES and DES crypto engine
z CRC-16 (CRC-CCITT) and CRC-32 (IEEE
z 16-bit real time counter (RTC) with separate oscillator
z One twelve-channel, 12-bit, 2msps Analog to Digital Converter
z One two-channel, 12-bit, 1msps Digital to Analog Converter
z Two Analog Comparators with window compare function, and current sources
z External interrupts on all general purpose I/O pins
z Programmable watchdog timer with separate on-chip ultra low power oscillator
z QTouch
z Special microcontroller features
z Power-on reset and programmable brown-out detection
z Internal and external clock options with PLL and prescaler
z Programmable multilevel interrupt controller
z Five sleep modes
z Programming and debug interfaces
z I/O and packages
z 34 Programmable I/O pins
z 44 - lead TQFP
z 44 - pad VQFN/QFN
z 49 - ball VFBGA
z Operating voltage
z 1.6 – 3.6V
z Operating frequency
z 0 – 12MHz from 1.6V
z 0 – 32MHz from 2.7V
®
library support
z Capacitive touch buttons, sliders and wheels
z PDI (program and debug interface)
®
2
C and SMBus compatible)
802.3) generator
8387C–AVR–3/12
1. Ordering Information
Ordering code Flash (bytes) EEPROM (bytes) SRAM (bytes) Speed (MHz) Power supply Package
ATxmega128A4U-AU 128K + 4K 2K 8K
ATxmega128A4U-AUR
ATxmega64A4U-AU 64K + 4K 2K 4K
ATxmega64A4U-AUR
ATxmega32A4U-AU 128K + 4K 2K 4K
ATxmega32A4U-AUR
ATxmega16A4U-AU 16K + 4K 2K 2K
ATxmega16A4U-AUR
ATxmega128A4U-MH 128K + 4K 2K 8K
ATxmega128A4U-MHR
ATxmega64A4U-MH 64K + 4K 2K 4K
ATxmega64A4U-MHR
ATxmega32A4U-MH 128K + 4K 2K 4K
ATxmega32A4U-MHR
ATxmega16A4U-MH 16K + 4K 2K 2K
ATxmega16A4U-MHR
ATxmega128A4U-CU 128K + 8K 2K 8K
ATxmega128A4U-CUR
ATxmega64A4U-CU 64K + 4K 2K 4K
ATxmega64A4U-CUR
ATxmega32A4U-CU 128K + 4K 1K 4K
ATxmega32A4U-CUR
ATxmega16A4U-CU 16K + 4K 1K 2K
ATxmega16A4U-CUR
(4)
(4)
(4)
(4)
(4)
(4)
(4)
(4)
(4)
(4)
(4)
(4)
128K + 4K 2K 8K
64K + 4K 4K 4K
128K + 4K 2K 4K
16K + 4K 2K 2K
128K + 4K 2K 8K
64K + 4K 4K 4K
128K + 4K 2K 4K
16K + 4K 2K 2K
128K + 8K 2K 8K
64K + 4K 2K 4K
128K + 4K 1K 4K
16K + 4K 1K 2K
32 1.6 - 3.6V
44A
PW
44M1
49C2
(1)(2)(3)
Tem p.
-40°C - 85°C
Notes: 1. This device can also be supplied in wafer form. Please contact your local Atmel sales office for detailed ordering information.
2. Pb-free packaging, complies to the European Directive for Restriction of Hazardous Substances (RoHS directive). Also Halide free and fully Green.
3. For packaging information, see “Instruction Set Summary” on page 62.
4. Tape and Reel
Package Type
44A 44-Lead, 10 x 10mm body size, 1.0mm body thickness, 0.8mm lead pitch, thin profile plastic quad flat package (TQFP)
44M1 44-Pad, 7x7x1mm body, lead pitch 0.50mm, 5.20mm exposed pad, t hermally enhanced plastic very thin quad no lead package (VQFN)
PW 44-Pad, 7x7x1mm body, lead pitch 0.50mm, 5.20mm exposed pad, thermally enhanced plastic very thin quad no lead package (VQFN)
49C2 49-Ball (7 x 7 Array), 0.65mm Pitch, 5.0 x 5.0 x 1.0mm, very thin, fine-pitch ball grid array package (VFBGA)
Typical Applications
Industrial control Climate control Low power battery applications
Factory automation RF and ZigBee
®
Power tools
Building control USB connectivity HVAC
Board control Sensor control Utility metering
White goods Optical Medical applications
XMEGA A4U [DATASHEET]
2
8387C–AVR–3/12
2. Pinout/Block Diagram
1
2
3
4
44
43
42
41
40
39
38
5
6
7
8
9
10
11
33
32
31
30
29
28
27
26
25
24
23
37
36
35
34
12
13
14
15
16
17
18
19
20
21
22
PA0
PA1
PA2
PA3
PA4
PB0
PB1
PB3
PB2
PA7
PA6
PA5
GND
VCC
PC0
VDD
GND
PC1
PC2
PC3
PC4
PC5
PC6
PC7
PD0
PD1
PD2
PD3
PD4
PD5
PD6
VCC
GND
PD7
PE0
PE1
PE2
PE3
RESET/PDI
PDI
PR0
PR1
AVCC
GND
Power
Supervision
Port A
EVENT ROUTING NETWORK
DMA
Controller
BUS
matrix
SRAMFLASH
ADC
AC0:1
OCD
Port EPort D
Prog/Debug
Interface
EEPROM
Port C
TC0:1
Event System
Controller
Watchdog
Timer
Watchdog
OSC/CLK
Control
Real Time
Counter
Interrupt
Controller
DATA BUS
DATA BUS
Port R
USART0:1
TWI
SPI
TC0:1
USART0:1
SPI
TC0
USART0
TWI
Port B
DAC
AREF
AREF
Sleep
Controller
Reset
Controller
IRCOM
Crypto /
CRC
USB
CPU
Internal
references
Internal
oscillators
XOSC TOSC
Digital function
Analog function / Oscillators
Programming, debug, test
External clock / Crystal pins
General Purpose I /O
Ground
Power
Figure 2-1. Block Diagram and QFN/TQFP pinout
Note: 1. For full details on pinout and pin functions refer to “Pinout and Pin Functions” on page 55.
XMEGA A4U [DATASHEET]
3
8387C–AVR–3/12
Figure 2-2. BGA pinout
Top view
1 234567
A
B
C
D
E
F
G
Bottom view
7654321
Table 2-1. BGA pinout
1 2 3 4 5 6 7
A PA3 AV CC GND PR1 PR0 PDI_DATA PE3
B PA4 PA1 PA0 GND
RESET/
PDI_CLK
PE2 VCC
C PA5 PA2 PA6 PA7 GND PE1 GND
D PB1 PB2 PB3 PB0 GND PD7 PE0
E GND GND PC3 GND PD4 PD5 PD6
A
B
C
D
E
F
G
F VCC PC0 PC4 PC6 PD0 PD1 PD3
G PC1 PC2 PC5 PC7 GND VCC PD2
XMEGA A4U [DATASHEET]
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4
3. Overview
The Atmel AVR XMEGA is a family of low power, high performance, and peripheral rich 8/16-bit microcontrollers based
on the AVR enhanced RISC architecture. By executing instructions in a single clock cycle, the AVR XMEGA devices
achieve CPU throughput approaching one million instructions per second (MIPS) per megahertz, allowing the system
designer to optimize power consumption versus processing speed.
The AVR CPU combines a rich instruction set with 32 general purpose working registers. All 32 registers are directly
connected to the arithmetic logic unit (ALU), allowing two independent registers to be accessed in a single instruction,
executed in one clock cycle. The resulting architecture is more code efficient while achieving throughputs many times
faster than conventional single-accumulator or CISC based microcontrollers.
The AVR XMEGA A4U devices provide the following features: in-system programmable flash with read-while-write
capabilities; internal EEPROM and SRAM; four-channel DMA controller, eight-channel event system and programmable
multilevel interrupt controller, 34 general purpose I/O lines, 16-bit real-time counter (RTC); five flexible, 16-bit
timer/counters with compare and PWM channels; five USARTs; two two-wire serial interfaces (TWIs); one full speed
USB 2.0 interface; two serial peripheral interfaces (SPIs); AES and DES cryptographic engine; one twelve-channel, 12bit ADC with programmable gain; one 2-channel 12-bit DAC; two analog comparators (ACs) with window mode;
programmable watchdog timer with separate internal oscillator; accurate internal oscillators with PLL and prescaler; and
programmable brown-out detection.
The program and debug interface (PDI), a fast, two-pin interface for programming and debugging, is available.
The ATx devices have five software selectable power saving modes. The idle mode stops the CPU while allowing the
SRAM, DMA controller, event system, interrupt controller, and all peripherals to continue functioning. The power-down
mode saves the SRAM and register contents, but stops the oscillators, disabling all other functions until the next TWI,
USB resume, or pin-change interrupt, or reset. In power-save mode, the asynchronous real-time counter continues to
run, allowing the application to maintain a timer base while the rest of the device is sleeping. In standby mode, the
external crystal oscillator keeps running while the rest of the device is sleeping. This allows very fast startup from the
external crystal, combined with low power consumption. In extended standby mode, both the main oscillator and the
asynchronous timer continue to run. To further reduce power consumption, the peripheral clock to each individual
peripheral can optionally be stopped in active mode and idle sleep mode.
Atmel offers a free QTouch library for embedding capacitive touch buttons, sliders and wheels functionality into AVR
microcontrollers.
The devices are manufactured using Atmel high-density, nonvolatile memory technology. The program flash memory can
be reprogrammed in-system through the PDI. A boot loader running in the device can use any interface to download the
application program to the flash memory. The boot loader software in the boot flash section will continue to run while the
application flash section is updated, providing true read-while-write operation. By combining an 8/16-bit RISC CPU with
in-system, self-programmable flash, the AVR XMEGA is a powerful microcontroller family that provides a highly flexible
and cost effective solution for many embedded applications.
All Atmel AVR XMEGA devices are supported with a full suite of program and system development tools, including C
compilers, macro assemblers, program debugger/simulators, programmers, and evaluation kits.
XMEGA A4U [DATASHEET]
8387C–AVR–3/12
5
3.1 Block Diagram
Power
Supervision
POR/BOD &
RESET
PORT A (8)
PORT B (8)
DMA
Controller
SRAM
ADCA
ACA
DACB
OCD
Int. Refs.
PDI
PA[0..7]
PB[0..7]
Watchdog
Timer
Watchdog
Oscillator
Interrupt
Controller
DATA BUS
Prog/Debug
Controller
VCC
GND
Oscillator
Circuits/
Clock
Generation
Oscillator
Control
Real Time
Counter
Event System
Controller
AREFA
AREFB
PDI_DATA
RESET/
PDI_CLK
Sleep
Controller
DES
CRC
PORT C (8)
PC[0..7]
TCC0:1
USARTC0:1
TWIC
SPIC
PD[0..7] PE[0..3]
PORT D (8)
TCD0:1
USARTD0:1
SPID
TCE0
USARTE0
TWIE
PORT E (4)
Tempref
AES
USB
PORT R (2)
DATA BUS
NVM Controller
MORPEEhsalF
IRCOM
BUS Matrix
CPU
EVENT ROUTING NETWORK
XTAL1/
TOSC1
XTAL2/
TOSC2
PR[0..1]
TOSC1 (optional)
TOSC2
(optional)
Digital function
Analog function
Programming, debug, test
Oscillator/Crystal/Cloc k
General Purpose I/O
Figure 3-1. XMEGA A4U Block Diagram
XMEGA A4U [DATASHEET]
8387C–AVR–3/12
6
4. Resources
A comprehensive set of development tools, application notes and datasheets are available for download on
http://www.atmel.com/avr.
4.1 Recommended reading
z Atmel AVR XMEGA AU manual
z XMEGA application notes
This device data sheet only contains part specific information with a short description of each peripheral and module. The
XMEGA AU manual describes the modules and peripherals in depth. The XMEGA application notes contain example
code and show applied use of the modules and peripherals.
All documentation are available from www.atmel.com/avr.
XMEGA A4U [DATASHEET]
8387C–AVR–3/12
7
5. Capacitive touch sensing
The Atmel QTouch library provides a simple to use solution to realize touch sensitive interfaces on most Atmel AVR
microcontrollers. The patented charge-transfer signal acquisition offers robust sensing and includes fully debounced
reporting of touch keys and includes Adjacent Key Suppression
events. The QTouch library includes support for the QTouch and QMatrix acquisition methods.
Touch sensing can be added to any application by linking the appropriate Atmel QTouch library for the AVR
microcontroller. This is done by using a simple set of APIs to define the touch channels and sensors, and then calling the
touch sensing API’s to retrieve the channel information and determine the touch sensor states.
The QTouch library is FREE and downloadable from the Atmel website at the following location:
www.atmel.com/qtouchlibrary. For implementation details and other information, refer to the QTouch library user guide -
also available for download from the Atmel website.
®
(AKS®) technology for unambiguous detection of key
XMEGA A4U [DATASHEET]
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8
6. AVR CPU
6.1 Features
• 8/16-bit, high-performance Atmel AVR RISC CPU
– 142 instructions
– Hardware multiplier
• 32x8-bit registers directly connected to the ALU
• Stack in RAM
• Stack pointer accessible in I/O memory space
• Direct addressing of up to 16MB of program memory and 16MB of data memory
• True 16/24-bit access to 16/24-bit I/O registers
• Efficient support for 8-, 16-, and 32-bit arithmetic
• Configuration change protection of system-critical features
6.2 Overview
All Atmel AVR XMEGA devices use the 8/16-bit AVR CPU. The main function of the CPU is to execute the code and
perform all calculations. The CPU is able to access memories, perform calculations, control peripherals, and execute the
program in the flash memory. Interrupt handling is described in a separate section, refer to “Interrupts and Programmable
Multilevel Interrupt Controller” on page 28.
6.3 Architectural Overview
In order to maximize performance and parallelism, the AVR CPU uses a Harvard architecture with separate memories
and buses for program and data. Instructions in the program memory are executed with single-level pipelining. While one
instruction is being executed, the next instruction is pre-fetched from the program memory. This enables instructions to
be executed on every clock cycle. For details of all AVR instructions, refer to http://www.atmel.com/avr.
Figure 6-1. Block diagram of the AVR CPU architecture.
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 in the ALU. After an arithmetic operation, the status register is
updated to reflect information about the result of the operation.
XMEGA A4U [DATASHEET]
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9
The ALU is directly connected to the fast-access register file. The 32 x 8-bit general purpose working registers all have
single clock cycle access time allowing single-cycle arithmetic logic unit (ALU) operation between registers or between a
register and an immediate. Six of the 32 registers can be used as three 16-bit address pointers for program and data
space addressing, enabling efficient address calculations.
The memory spaces are linear. The data memory space and the program memory space are two different memory
spaces.
The data memory space is divided into I/O registers, SRAM, and external RAM. In addition, the EEPROM can be
memory mapped in the data memory.
All I/O status and control registers reside in the lowest 4KB addresses of the data memory. This is referred to as the I/O
memory space. The lowest 64 addresses can be accessed directly, or as the data space locations from 0x00 to 0x3F.
The rest is the extended I/O memory space, ranging from 0x0040 to 0x0FFF. I/O registers here must be accessed as
data space locations using load (LD/LDS/LDD) and store (ST/STS/STD) instructions.
The SRAM holds data. Code execution from SRAM is not supported. It can easily be accessed through the five different
addressing modes supported in the AVR architecture. The first SRAM address is 0x2000.
Data addresses 0x1000 to 0x1FFF are reserved for memory mapping of EEPROM.
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 selfprogramming of the application flash memory must reside in the boot program section. The application section contains
an application table section with separate lock bits for write and read/write protection. The application table section can
be used for safe storing of nonvolatile data in the program memory.
6.4 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 32 general
purpose registers. In a single clock cycle, arithmetic operations between general purpose registers or between a register
and an immediate are executed and the result is stored in the register file. After an arithmetic or logic operation, the
status register is updated to reflect information about the result of the operation.
ALU operations are divided into three main categories – arithmetic, logical, and bit functions. Both 8- and 16-bit
arithmetic is supported, and the instruction set allows for efficient implementation of 32-bit aritmetic. The hardware
multiplier supports signed and unsigned multiplication and fractional format.
6.4.1 Hardware Multiplier
The multiplier is capable of multiplying two 8-bit numbers into a 16-bit result. The hardware multiplier supports different
variations of signed and unsigned integer and fractional numbers:
z Multiplication of unsigned integers
z Multiplication of signed integers
z Multiplication of a signed integer with an unsigned integer
z Multiplication of unsigned fractional numbers
z Multiplication of signed fractional numbers
z Multiplication of a signed fractional number with an unsigned one
A multiplication takes two CPU clock cycles.
6.5 Program Flow
After reset, the CPU starts to execute instructions from the lowest address in the flash programmemory ‘0.’ The program
counter (PC) addresses the next instruction to be fetched.
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Program flow is provided by conditional and unconditional jump and call instructions capable of addressing the whole
address space directly. Most AVR instructions use a 16-bit word format, while a limited number use a 32-bit format.
During interrupts and subroutine calls, the return address PC is stored on the stack. The stack is 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. After
reset, the stack pointer (SP) points to the highest address in the internal SRAM. The SP is read/write accessible in the
I/O memory space, enabling easy implementation of multiple stacks or stack areas. The data SRAM can easily be
accessed through the five different addressing modes supported in the AVR CPU.
6.6 Status Register
The status register (SREG) contains information about the result of the most recently executed arithmetic or logic
instruction. This information can be used for altering program flow in order to perform conditional operations. Note that
the status register is updated after all ALU operations, as specified in the instruction set reference. This will in many
cases remove the need for using the dedicated compare instructions, resulting in faster and more compact code.
The status register is not automatically stored when entering an interrupt routine nor restored when returning from an
interrupt. This must be handled by software.
The status register is accessible in the I/O memory space.
6.7 Stack and Stack Pointer
The stack is used for storing return addresses after interrupts and subroutine calls. It can also be used for storing
temporary data. The stack pointer (SP) register always points to the top of the stack. It is implemented as two 8-bit
registers that are accessible in the I/O memory space. Data are pushed and popped from the stack using the PUSH and
POP instructions. The stack grows from a higher memory location to a lower memory location. This implies that pushing
data onto the stack decreases the SP, and popping data off the stack increases the SP. The SP is automatically loaded
after reset, and the initial value is the highest address of the internal SRAM. If the SP is changed, it must be set to point
above address 0x2000, and it must be defined before any subroutine calls are executed or before interrupts are enabled.
During interrupts or subroutine calls, the return address is automatically pushed on the stack. The return address can be
two or three bytes, depending on program memory size of the device. For devices with 128KB or less of program
memory, the return address is two bytes, and hence the stack pointer is decremented/incremented by two. For devices
with more than 128KB of program memory, the return address is three bytes, and hence the SP is
decremented/incremented by three. The return address is popped off the stack when returning from interrupts using the
RETI instruction, and from subroutine calls using the RET instruction.
The SP is decremented by one when data are pushed on the stack with the PUSH instruction, and incremented by one
when data is popped off the stack using the POP instruction.
To prevent corruption when updating the stack pointer from software, a write to SPL will automatically disable interrupts
for up to four instructions or until the next I/O memory write.
After reset the stack pointer is initialized to the highest address of the SRAM. See Figure 7-3 on page 15.
6.8 Register File
The register file consists of 32 x 8-bit general purpose working registers with single clock cycle access time. The register
file supports the following input/output schemes:
z One 8-bit output operand and one 8-bit result input
z Two 8-bit output operands and one 8-bit result input
z Two 8-bit output operands and one 16-bit result input
z One 16-bit output operand and one 16-bit result input
Six of the 32 registers can be used as three 16-bit address register pointers for data space addressing, enabling efficient
address calculations. One of these address pointers can also be used as an address pointer for lookup tables in flash
program memory.
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7. Memories
7.1 Features
• Flash program memory
– One linear address space
– In-system programmable
– Self-programming and boot loader support
– Application section for application code
– Application table section for application code or data storage
– Boot section for application code or boot loader code
– Separate read/write protection lock bits for all sections
– Built in fast CRC check of a selectable flash program memory section
• Data memory
– One linear address space
– Single-cycle access from CPU
– SRAM
– EEPROM
Byte and page accessible
Optional memory mapping for direct load and store
– I/O memory
Configuration and status registers for all peripherals and modules
16 bit-accessible general purpose registers for global variables or flags
– Bus arbitration
Deterministic priority handling between CPU, DMA controller, and other bus masters
– Separate buses for SRAM, EEPROM and I/O memory
Simultaneous bus access for CPU and DMA controller
• Production signature row memory for factory programmed data
– ID for each microcontroller device type
– Serial number for each device
– Calibration bytes for factory calibrated peripherals
• User signature row
– One flash page in size
– Can be read and written from software
– Content is kept after chip erase
7.2 Overview
The Atmel AVR architecture has two main memory spaces, the program memory and the data memory. Executable code
can reside only in the program memory, while data can be stored in the program memory and the data memory. The data
memory includes the internal SRAM, and EEPROM for nonvolatile data storage. All memory spaces are linear and
require no memory bank switching. Nonvolatile memory (NVM) spaces can be locked for further write and read/write
operations. This prevents unrestricted access to the application software.
A separate memory section contains the fuse bytes. These are used for configuring important system functions, and can
only be written by an external programmer.
The available memory size configurations are shown in
Flash memory signature row for calibration data, device identification, serial number etc.
“Ordering Information” on page 2. In addition, each device has a
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7.3 Flash Program Memory
The Atmel AVR XMEGA devices contain on-chip, in-system reprogrammable flash memory for program storage. The
flash memory can be accessed for read and write from an external programmer through the PDI or from application
software running in the device.
All AVR CPU instructions are 16 or 32 bits wide, and each flash location is 16 bits wide. The flash memory is organized
in two main sections, the application section and the boot loader section. The sizes of the different sections are fixed, but
device-dependent. These two sections have separate lock bits, and can have different levels of protection. The store
program memory (SPM) instruction, which is used to write to the flash from the application software, will only operate
when executed from the boot loader section.
The application section contains an application table section with separate lock settings. This enables safe storage of
nonvolatile data in the program memory.
Figure 7-1. Flash Program Memory (Hexadecimal address).
ATxmega128A4U ATxmega64A4U ATxmega32A4U ATxmega16A4U
Word Address
0 0 0 0
EFFF / 77FF / 37FF / 17FF
F000 / 7800 / 3800 / 1800
FFFF / 7FFF / 3FFF / 1FFF
10000 / 8000 / 4000 / 2000
10FFF / 87FF / 47FF / 27FF
7.3.1 Application Section
The Application section is the section of the flash that is used for storing the executable application code. The protection
level for the application section can be selected by the boot lock bits for this section. The application section can not store
any boot loader code since the SPM instruction cannot be executed from the application section.
7.3.2 Application Table Section
The application table section is a part of the application section of the flash memory that can be used for storing data.
The size is identical to the boot loader section. The protection level for the application table section can be selected by
the boot lock bits for this section. The possibilities for different protection levels on the application section and the
application table section enable safe parameter storage in the program memory. If this section is not used for data,
application code can reside here.
Application Section
(128K/64K/32K/16K)
...
Application Table Section
(4K/4K/4K/4K)
Boot Section
(8K/4K/4K/4K)
7.3.3 Boot Loader Section
While the application section is used for storing the application code, the boot loader software must be located in the boot
loader section because the SPM instruction can only initiate programming when executing from this section. The SPM
instruction can access the entire flash, including the boot loader section itself. The protection level for the boot loader
section can be selected by the boot loader lock bits. If this section is not used for boot loader software, application code
can be stored here.
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7.3.4 Production Signature Row
The production signature row is a separate memory section for factory programmed data. It contains calibration data for
functions such as oscillators and analog modules. Some of the calibration values will be automatically loaded to the
corresponding module or peripheral unit during reset. Other values must be loaded from the signature row and written to
the corresponding peripheral registers from software. For details on calibration conditions, refer to “Electrical
Characteristics” on page 71.
The production signature row also contains an ID that identifies each microcontroller device type and a serial number for
each manufactured device. The serial number consists of the production lot number, wafer number, and wafer
coordinates for the device. The device ID for the available devices is shown in Table 7-2.
The production signature row cannot be written or erased, but it can be read from application software and external
programmers.
Figure 7-2. Device ID bytes for Atmel AVR XMEGA A4U devices.
Device Device ID bytes
ATxmega16A4U 41 94 1E
ATxmega32A4U 41 95 1E
ATxmega64A4U 46 96 1E
ATxmega128A4U 46 97 1E
Byte 2 Byte 1 Byte 0
7.3.5 User Signature Row
The user signature row is a separate memory section that is fully accessible (read and write) from application software
and external programmers. It is one flash page in size, and is meant for static user parameter storage, such as calibration
data, custom serial number, identification numbers, random number seeds, etc. This section is not erased by chip erase
commands that erase the flash, and requires a dedicated erase command. This ensures parameter storage during
multiple program/erase operations and on-chip debug sessions.
7.4 Fuses and Lock bits
The fuses are used to configure important system functions, and can only be written from an external programmer. The
application software can read the fuses. The fuses are used to configure reset sources such as brownout detector and
watchdog, startup configuration, JTAG enable, and JTAG user ID.
The lock bits are used to set protection levels for the different flash sections (that is, if read and/or write access should be
blocked). Lock bits can be written by external programmers and application software, but only to stricter protection levels.
Chip erase is the only way to erase the lock bits. To ensure that flash contents are protected even during chip erase, the
lock bits are erased after the rest of the flash memory has been erased.
An unprogrammed fuse or lock bit will have the value one, while a programmed fuse or lock bit will have the value zero.
Both fuses and lock bits are reprogrammable like the flash program memory.
7.5 Data Memory
The data memory contains the I/O memory, internal SRAM, optionally memory mapped EEPROM, and external memory
if available. The data memory is organized as one continuous memory section, see Figure 7-3. To simplify development,
I/O Memory, EEPROM and SRAM will always have the same start addresses for all Atmel AVR XMEGA devices.
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Figure 7-3. Data memory map (Hexadecimal address).
Byte Address ATxmega64A4U Byte Address ATxmega32A4U Byte Address ATxmega16A4U
0
I/O Registers (4K)
FFF FFF FFF
1000
EEPROM (2K)
17FF 13FF 13FF
RESERVED RESERVED RESERVED
2000
Internal SRAM (4K)
2FFF 2FFF 27FF
Byte Address ATxmega128A4U
0
I/O Registers (4K)
FFF
1000
EEPROM (2K)
17FF
RESERVED
2000
Internal SRAM (8K)
3FFF
1000
2000
0
I/O Registers (4K)
EEPROM (1K)
Internal SRAM (4K)
0
I/O Registers (4K)
1000
EEPROM (1K)
2000
Internal SRAM (2K)
7.6 EEPROM
All devices have EEPROM for nonvolatile data storage. It is either addressable in a separate data space (default) or
memory mapped and accessed in normal data space. The EEPROM supports both byte and page access. Memory
mapped EEPROM allows highly efficient EEPROM reading and EEPROM buffer loading. When doing this, EEPROM is
accessible using load and store instructions. Memory mapped EEPROM will always start at hexadecimal address
0x1000.
7.7 I/O Memory
The status and configuration registers for peripherals and modules, including the CPU, are addressable through I/O
memory locations. All I/O locations can be accessed by the load (LD/LDS/LDD) and store (ST/STS/STD) instructions,
which are used to transfer data between the 32 registers in the register file and the I/O memory. The IN and OUT
instructions can address I/O memory locations in the range of 0x00 to 0x3F directly. In the address range 0x00 - 0x1F,
single-cycle instructions for manipulation and checking of individual bits are available.
The I/O memory address for all peripherals and modules in XMEGA A4U is shown in the “Peripheral Module Address
Map” on page 60.
7.7.1 General Purpose I/O Registers
The lowest 16 I/O memory addresses are reserved as general purpose I/O registers. These registers can be used for
storing global variables and flags, as they are directly bit-accessible using the SBI, CBI, SBIS, and SBIC instructions.
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7.8 Data Memory and Bus Arbitration
Since the data memory is organized as four separate sets of memories, the different bus masters (CPU, DMA controller
read and DMA controller write, etc.) can access different memory sections at the same time.
7.9 Memory Timing
Read and write access to the I/O memory takes one CPU clock cycle. A write to SRAM takes one cycle, and a read from
SRAM takes two cycles. For burst read (DMA), new data are available every cycle. EEPROM page load (write) takes one
cycle, and three cycles are required for read. For burst read, new data are available every second cycle. Refer to the
instruction summary for more details on instructions and instruction timing.
7.10 Device ID and Revision
Each device has a three-byte device ID. This ID identifies Atmel as the manufacturer of the device and the device type. A
separate register contains the revision number of the device.
7.11 I/O Memory Protection
Some features in the device are regarded as critical for safety in some applications. Due to this, it is possible to lock the
I/O register related to the clock system, the event system, and the advanced waveform extensions. As long as the lock is
enabled, all related I/O registers are locked and they can not be written from the application software. The lock registers
themselves are protected by the configuration change protection mechanism.
7.12 Flash and EEPROM Page Size
The flash program memory and EEPROM data memory are organized in pages. The pages are word accessible for the
flash and byte accessible for the EEPROM.
Table 7-1 on page 16 shows the Flash Program Memory organization and Program Counter (PC) size. Flash write and
erase operations are performed on one page at a time, while reading the Flash is done one byte at a time. For Flash
access the Z-pointer (Z[m:n]) is used for addressing. The most significant bits in the address (FPAGE) give the page
number and the least significant address bits (FWORD) give the word in the page.
Table 7-1. Number of words and pages in the flash.
Devices PC size Flash size Page Size FWORD FPAGE Application Boot
bits bytes words Size
ATxmega16A4U 14 16K + 4K 128 Z[6:0] Z[13:7] 16K 64 4K 16
ATxmega32A4U 15 32K + 4K 128 Z[6:0] Z[14:7] 32K 128 4K 16
ATxmega64A4U 16 64K + 4K 128 Z[6:0] Z[15:7] 64K 256 4K 16
ATxmega128A4U 17 128K + 8K 128 Z[8:0] Z[16:7] 128K 512 8K 32
No of
pages
Size
No of
pages
Table 7-2 shows EEPROM memory organization for the Atmel AVR XMEGA A4U devices. EEEPROM write and erase
operations can be performed one page or one byte at a time, while reading the EEPROM is done one byte at a time. For
EEPROM access the NVM address register (ADDR[m:n]) is used for addressing. The most significant bits in the address
(E2PAGE) give the page number and the least significant address bits (E2BYTE) give the byte in the page.
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Table 7-2. Number of bytes and pages in the EEPROM.
Devices EEPROM Page Size E2BYTE E2PAGE No of Pages
Size bytes
ATxmega16A4U 1K 32 ADDR[4:0] ADDR[10:5] 32
ATxmega32A4U 1K 32 ADDR[4:0] ADDR[10:5] 32
ATxmega64A4U 2K 32 ADDR[4:0] ADDR[10:5] 64
ATxmega128A4U 2K 32 ADDR[4:0] ADDR[10:5] 64
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8. DMAC – Direct Memory Access Controller
8.1 Features
• Allows high speed data transfers with minimal CPU intervention
– from data memory to data memory
– from data memory to peripheral
– from peripheral to data memory
– from peripheral to peripheral
• Four DMA channels with separate
– transfer triggers
– interrupt vectors
– addressing modes
• Programmable channel priority
• From 1 byte to 16MB of data in a single transaction
– Up to 64KB block transfers with repeat
– 1, 2, 4, or 8 byte burst transfers
• Multiple addressing modes
– Static
–Incremental
– Decremental
• Optional reload of source and destination addresses at the end of each
–Burst
–Block
– Transaction
• Optional interrupt on end of transaction
• Optional connection to CRC generator for CRC on DMA data
8.2 Overview
The four-channel direct memory access (DMA) controller can transfer data between memories and peripherals, and thus
offload these tasks from the CPU. It enables high data transfer rates with minimum CPU intervention, and frees up CPU
time. The four DMA channels enable up to four independent and parallel transfers.
The DMA controller can move data between SRAM and peripherals, between SRAM locations and directly between
peripheral registers. With access to all peripherals, the DMA controller can handle automatic transfer of data to/from
communication modules. The DMA controller can also read from memory mapped EEPROM.
Data transfers are done in continuous bursts of 1, 2, 4, or 8 bytes. They build block transfers of configurable size from 1
byte to 64KB. A repeat counter can be used to repeat each block transfer for single transactions up to 16MB. Source and
destination addressing can be static, incremental or decremental. Automatic reload of source and/or destination
addresses can be done after each burst or block transfer, or when a transaction is complete. Application software,
peripherals, and events can trigger DMA transfers.
The four DMA channels have individual configuration and control settings. This include source, destination, transfer
triggers, and transaction sizes. They have individual interrupt settings. Interrupt requests can be generated when a
transaction is complete or when the DMA controller detects an error on a DMA channel.
To allow for continuous transfers, two channels can be interlinked so that the second takes over the transfer when the
first is finished, and vice versa.
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9. Event System
9.1 Features
• System for direct peripheral-to-peripheral communication and signaling
• Peripherals can directly send, receive, and react to peripheral events
– CPU and DMA controller independent operation
– 100% predictable signal timing
– Short and guaranteed response time
• Eight event channels for up to eight different and parallel signal routing configurations
• Events can be sent and/or used by most peripherals, clock system, and software
• Additional functions include
– Quadrature decoders
– Digital filtering of I/O pin state
• Works in active mode and idle sleep mode
9.2 Overview
The event system enables direct peripheral-to-peripheral communication and signaling. It allows a change in one
peripheral’s state to automatically trigger actions in other peripherals. It is designed to provide a predictable system for
short and predictable response times between peripherals. It allows for autonomous peripheral control and interaction
without the use of interrupts, CPU, or DMA controller resources, and is thus a powerful tool for reducing the complexity,
size and execution time of application code. It also allows for synchronized timing of actions in several peripheral
modules.
A change in a peripheral’s state is referred to as an event, and usually corresponds to the peripheral’s interrupt
conditions. Events can be directly passed to other peripherals using a dedicated routing network called the event routing
network. How events are routed and used by the peripherals is configured in software.
Figure 9-1 on page 19 shows a basic diagram of all connected peripherals. The event system can directly connect
together analog and digital converters, analog comparators, I/O port pins, the real-time counter, timer/counters, IR
communication module (IRCOM), and USB interface. It can also be used to trigger DMA transactions (DMA controller).
Events can also be generated from software and the peripheral clock.
Figure 9-1. Event system overview and connected peripherals.
ADC
AC
DAC
CPU /
Software
Event Routing Network
System
Controller
Port pins
Event
DMA
Controller
IRCOM
clk
PER
Prescaler
Real Time
Counter
Timer /
Counters
USB
The event routing network consists of eight software-configurable multiplexers that control how events are routed and
used. These are called event channels, and allow for up to eight parallel event routing configurations. The maximum
routing latency is two peripheral clock cycles. The event system works in both active mode and idle sleep mode.
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10. System Clock and Clock options
10.1 Features
• Fast start-up time
• Safe run-time clock switching
• Internal oscillators:
– 32MHz run-time calibrated and tuneable oscillator
– 2MHz run-time calibrated oscillator
– 32.768kHz calibrated oscillator
– 32kHz ultra low power (ULP) oscillator with 1kHz output
• External clock options
– 0.4MHz - 16MHz crystal oscillator
– 32.768kHz crystal oscillator
– External clock
• PLL with 20MHz - 128MHz output frequency
– Internal and external clock options and 1x to 31x multiplication
– Lock detector
• Clock prescalers with 1x to 2048x division
• Fast peripheral clocks running at two and four times the CPU clock
• Automatic run-time calibration of internal oscillators
• External oscillator and PLL lock failure detection with optional non-maskable interrupt
10.2 Overview
Atmel AVR XMEGA A4U devices have a flexible clock system supporting a large number of clock sources. It
incorporates both accurate internal oscillators and external crystal oscillator and resonator support. A high-frequency
phase locked loop (PLL) and clock prescalers can be used to generate a wide range of clock frequencies. A calibration
feature (DFLL) is available, and can be used for automatic run-time calibration of the internal oscillators to remove
frequency drift over voltage and temperature. An oscillator failure monitor can be enabled to issue a non-maskable
interrupt and switch to the internal oscillator if the external oscillator or PLL fails.
When a reset occurs, all clock sources except the 32kHz ultra low power oscillator are disabled. After reset, the device
will always start up running from the 2MHz internal oscillator. During normal operation, the system clock source and
prescalers can be changed from software at any time.
Figure 10-1 on page 21 presents the principal clock system in the XMEGA A4U family of devices. Not all of the clocks
need to be active at a given time. The clocks for the CPU and peripherals can be stopped using sleep modes and power
reduction registers, as described in “Power Management and Sleep Modes” on page 23.
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Figure 10-1. The clock system, clock sources and clock distribution.
Real Time
Counter
Peripherals
RAM AVR CPU
Non-Volatile
Memory
Watchdog
Timer
Brown-out
Detector
System Clock Prescalers
USB
Prescaler
System Clock Multiplexer
(SCLKSEL)
PLLSRC
RTCSRC
DIV32
32 kHz
Int. ULP
32.768 kHz
Int. OSC
32.768 kHz
TOSC
2 MHz
Int. Osc
32 MHz
Int. Osc
0.4 – 16 MHz
XTAL
DIV32
DIV32
DIV4
XOSCSEL
PLL
USBSRC
TOSC1
TOSC2
XTAL1
XTAL2
clk
SYS
clk
RTC
clk
PER2
clk
PER
clk
CPU
clk
PER4
clk
USB
10.3 Clock Sources
The clock sources are divided in two main groups: internal oscillators and external clock sources. Most of the clock
sources can be directly enabled and disabled from software, while others are automatically enabled or disabled,
depending on peripheral settings. After reset, the device starts up running from the 2MHz internal oscillator. The other
clock sources, DFLLs and PLL, are turned off by default.
The internal oscillators do not require any external components to run. For details on characteristics and accuracy of the
internal oscillators, refer to the device datasheet.
10.3.1 32kHz Ultra Low Power Internal Oscillator
This oscillator provides an approximate 32kHz clock. The 32kHz ultra low power (ULP) internal oscillator is a very low
power clock source, and it is not designed for high accuracy. The oscillator employs a built-in prescaler that provides a
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1kHz output. The oscillator is automatically enabled/disabled when it is used as clock source for any part of the device.
This oscillator can be selected as the clock source for the RTC.
10.3.2 32.768kHz Calibrated Internal Oscillator
This oscillator provides an approximate 32.768kHz clock. It is calibrated during production to provide a default frequency
close to its nominal frequency. The calibration register can also be written from software for run-time calibration of the
oscillator frequency. The oscillator employs a built-in prescaler, which provides both a 32.768kHz output and a 1.024kHz
output.
10.3.3 32.768kHz Crystal Oscillator
A 32.768kHz crystal oscillator can be connected between the TOSC1 and TOSC2 pins and enables a dedicated low
frequency oscillator input circuit. A low power mode with reduced voltage swing on TOSC2 is available. This oscillator
can be used as a clock source for the system clock and RTC, and as the DFLL reference clock.
10.3.4 0.4 - 16MHz Crystal Oscillator
This oscillator can operate in four different modes optimized for different frequency ranges, all within 0.4 - 16MHz.
10.3.5 2MHz Run-time Calibrated Internal Oscillator
The 2MHz run-time calibrated internal oscillator is the default system clock source after reset. It is calibrated during
production to provide a default frequency close to its nominal frequency. A DFLL can be enabled for automatic run-time
calibration of the oscillator to compensate for temperature and voltage drift and optimize the oscillator accuracy.
10.3.6 32MHz Run-time Calibrated Internal Oscillator
The 32MHz run-time calibrated internal oscillator is a high-frequency oscillator. It is calibrated during production to
provide a default frequency close to its nominal frequency. A digital frequency looked loop (DFLL) can be enabled for
automatic run-time calibration of the oscillator to compensate for temperature and voltage drift and optimize the oscillator
accuracy. This oscillator can also be adjusted and calibrated to any frequency between 30MHz and 55MHz. The
production signature row contains 48MHz calibration values intended used when the oscillator is used a full-speed USB
clock source.
10.3.7 External Clock Sources
The XTAL1 and XTAL2 pins can be used to drive an external oscillator, either a quartz crystal or a ceramic resonator.
XTAL1 can be used as input for an external clock signal. The TOSC1 and TOSC2 pins is dedicated to driving a
32.768kHz crystal oscillator.
10.3.8 PLL with 1x-31x Multiplication Factor
The built-in phase locked loop (PLL) can be used to generate a high-frequency system clock. The PLL has a userselectable multiplication factor of from 1 to 31. In combination with the prescalers, this gives a wide range of output
frequencies from all clock sources.
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11. Power Management and Sleep Modes
11.1 Features
• Power management for adjusting power consumption and functions
• Five sleep modes
–Idle
–Power down
– Power save
–Standby
– Extended standby
• Power reduction register to disable clock and turn off unused peripherals in active and idle modes
11.2 Overview
Various sleep modes and clock gating are provided in order to tailor power consumption to application requirements.
This enables the Atmel AVR XMEGA microcontroller to stop unused modules to save power.
All sleep modes are available and can be entered from active mode. In active mode, the CPU is executing application
code. When the device enters sleep mode, program execution is stopped and interrupts or a reset is used to wake the
device again. The application code decides which sleep mode to enter and when. Interrupts from enabled peripherals
and all enabled reset sources can restore the microcontroller from sleep to active mode.
In addition, power reduction registers provide a method to stop the clock to individual peripherals from software. When
this is done, the current state of the peripheral is frozen, and there is no power consumption from that peripheral. This
reduces the power consumption in active mode and idle sleep modes and enables much more fine-tuned power
management than sleep modes alone.
11.3 Sleep Modes
Sleep modes are used to shut down modules and clock domains in the microcontroller in order to save power. XMEGA
microcontrollers have five different sleep modes tuned to match the typical functional stages during application
execution. A dedicated sleep instruction (SLEEP) is available to enter sleep mode. Interrupts are used to wake the
device from sleep, and the available interrupt wake-up sources are dependent on the configured sleep mode. When an
enabled interrupt occurs, the device will wake up and execute the interrupt service routine before continuing normal
program execution from the first instruction after the SLEEP instruction. If other, higher priority interrupts are pending
when the wake-up occurs, their interrupt service routines will be executed according to their priority before the interrupt
service routine for the wake-up interrupt is executed. After wake-up, the CPU is halted for four cycles before execution
starts.
The content of the register file, SRAM and registers are kept during sleep. If a reset occurs during sleep, the device will
reset, start up, and execute from the reset vector.
11.3.1 Idle Mode
In idle mode the CPU and nonvolatile memory are stopped (note that any ongoing programming will be completed), but
all peripherals, including the interrupt controller, event system and DMA controller are kept running. Any enabled
interrupt will wake the device.
11.3.2 Power-down Mode
In power-down mode, all clocks, including the real-time counter clock source, are stopped. This allows operation only of
asynchronous modules that do not require a running clock. The only interrupts that can wake up the MCU are the twowire interface address match interrupt, asynchronous port interrupts, and the USB resume interrupt.
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11.3.3 Power-save Mode
Power-save mode is identical to power down, with one exception. If the real-time counter (RTC) is enabled, it will keep
running during sleep, and the device can also wake up from either an RTC overflow or compare match interrupt.
11.3.4 Standby Mode
Standby mode is identical to power down, with the exception that the enabled system clock sources are kept running
while the CPU, peripheral, and RTC clocks are stopped. This reduces the wake-up time.
11.3.5 Extended Standby Mode
Extended standby mode is identical to power-save mode, with the exception that the enabled system clock sources are
kept running while the CPU and peripheral clocks are stopped. This reduces the wake-up time.
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12. System Control and Reset
12.1 Features
• Reset the microcontroller and set it to initial state when a reset source goes active
• Multiple reset sources that cover different situations
–Power-on reset
– External reset
– Watchdog reset
– Brownout reset
– PDI reset
– Software reset
• Asynchronous operation
– No running system clock in the device is required for reset
• Reset status register for reading the reset source from the application code
12.2 Overview
The reset system issues a microcontroller reset and sets the device to its initial state. This is for situations where
operation should not start or continue, such as when the microcontroller operates below its power supply rating. If a reset
source goes active, the device enters and is kept in reset until all reset sources have released their reset. The I/O pins
are immediately tri-stated. The program counter is set to the reset vector location, and all I/O registers are set to their
initial values. The SRAM content is kept. However, if the device accesses the SRAM when a reset occurs, the content of
the accessed location can not be guaranteed.
After reset is released from all reset sources, the default oscillator is started and calibrated before the device starts
running from the reset vector address. By default, this is the lowest program memory address, 0, but it is possible to
move the reset vector to the lowest address in the boot section.
The reset functionality is asynchronous, and so no running system clock is required to reset the device. The software
reset feature makes it possible to issue a controlled system reset from the user software.
The reset status register has individual status flags for each reset source. It is cleared at power-on reset, and shows
which sources have issued a reset since the last power-on.
12.3 Reset Sequence
A reset request from any reset source will immediately reset the device and keep it in reset as long as the request is
active. When all reset requests are released, the device will go through three stages before the device starts running
again:
z Reset counter delay
z Oscillator startup
z Oscillator calibration
If another reset requests occurs during this process, the reset sequence will start over again.
12.4 Reset Sources
12.4.1 Power-on Reset
A power-on reset (POR) is generated by an on-chip detection circuit. The POR is activated when the VCC rises and
reaches the POR threshold voltage (V
The POR is also activated to power down the device properly when the V
The V
level is higher for falling VCC than for rising VCC. Consult the datasheet for POR characteristics data.
POT
), and this will start the reset sequence.
POT
falls and drops below the V
CC
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12.4.2 Brownout Detection
The on-chip brownout detection (BOD) circuit monitors the VCC level during operation by comparing it to a fixed,
programmable level that is selected by the BODLEVEL fuses. If disabled, BOD is forced on at the lowest level during chip
erase and when the PDI is enabled.
12.4.3 External Reset
The external reset circuit is connected to the external RESET pin. The external reset will trigger when the RESET pin is
driven below the RESET
pin threshold voltage, V
held as long as the pin is kept low. The RESET
12.4.4 Watchdog Reset
The watchdog timer (WDT) is a system function for monitoring correct program operation. If the WDT is not reset from
the software within a programmable timeout period, a watchdog reset will be given. The watchdog reset is active for one
to two clock cycles of the 2MHz internal oscillator. For more details see “WDT – Watchdog Timer” on page 27.
12.4.5 Software Reset
The software reset makes it possible to issue a system reset from software by writing to the software reset bit in the reset
control register.The reset will be issued within two CPU clock cycles after writing the bit. It is not possible to execute any
instruction from when a software reset is requested until it is issued.
12.4.6 Program and Debug Interface Reset
The program and debug interface reset contains a separate reset source that is used to reset the device during external
programming and debugging. This reset source is accessible only from external debuggers and programmers.
, for longer than the minimum pulse period, t
RST
pin includes an internal pull-up resistor.
. The reset will be
EXT
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13. WDT – Watchdog Timer
13.1 Features
• Issues a device reset if the timer is not reset before its timeout period
• Asynchronous operation from dedicated oscillator
• 1kHz output of the 32kHz ultra low power oscillator
• 11 selectable timeout periods, from 8ms to 8s
• Two operation modes:
– Normal mode
– Window mode
• Configuration lock to prevent unwanted changes
13.2 Overview
The watchdog timer (WDT) is a system function for monitoring correct program operation. It makes it possible to recover
from error situations such as runaway or deadlocked code. The WDT is a timer, configured to a predefined timeout
period, and is constantly running when enabled. If the WDT is not reset within the timeout period, it will issue a
microcontroller reset. The WDT is reset by executing the WDR (watchdog timer reset) instruction from the application
code.
The window mode makes it possible to define a time slot or window inside the total timeout period during which WDT
must be reset. If the WDT is reset outside this window, either too early or too late, a system reset will be issued.
Compared to the normal mode, this can also catch situations where a code error causes constant WDR execution.
The WDT will run in active mode and all sleep modes, if enabled. It is asynchronous, runs from a CPU-independent clock
source, and will continue to operate to issue a system reset even if the main clocks fail.
The configuration change protection mechanism ensures that the WDT settings cannot be changed by accident. For
increased safety, a fuse for locking the WDT settings is also available.
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14. Interrupts and Programmable Multilevel Interrupt Controller
14.1 Features
• Short and predictable interrupt response time
• Separate interrupt configuration and vector address for each interrupt
• Programmable multilevel interrupt controller
– Interrupt prioritizing according to level and vector address
– Three selectable interrupt levels for all interrupts: low, medium and high
– Selectable, round-robin priority scheme within low-level interrupts
– Non-maskable interrupts for critical functions
• Interrupt vectors optionally placed in the application section or the boot loader section
14.2 Overview
Interrupts signal a change of state in peripherals, and this can be used to alter program execution. Peripherals can have
one or more interrupts, and all are individually enabled and configured. When an interrupt is enabled and configured, it
will generate an interrupt request when the interrupt condition is present. The programmable multilevel interrupt
controller (PMIC) controls the handling and prioritizing of interrupt requests. When an interrupt request is acknowledged
by the PMIC, the program counter is set to point to the interrupt vector, and the interrupt handler can be executed.
All peripherals can select between three different priority levels for their interrupts: low, medium, and high. Interrupts are
prioritized according to their level and their interrupt vector address. Medium-level interrupts will interrupt low-level
interrupt handlers. High-level interrupts will interrupt both medium- and low-level interrupt handlers. Within each level, the
interrupt priority is decided from the interrupt vector address, where the lowest interrupt vector address has the highest
interrupt priority. Low-level interrupts have an optional round-robin scheduling scheme to ensure that all interrupts are
serviced within a certain amount of time.
Non-maskable interrupts (NMI) are also supported, and can be used for system critical functions.
14.3 Interrupt vectors
The interrupt vector is the sum of the peripheral’s base interrupt address and the offset address for specific interrupts in
each peripheral. The base addresses for the Atmel AVR XMEGA A4U devices are shown in Table 14-1 on page 29.
Offset addresses for each interrupt available in the peripheral are described for each peripheral in the XMEGA AU
manual. For peripherals or modules that have only one interrupt, the interrupt vector is shown in Table 14-1 on page 29.
The program address is the word address.
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Table 14-1. Reset and interrupt vectors
Program address
(base address) Source Interrupt description
0x000 RESET
0x002 OSCF_INT_vect Crystal oscillator failure interrupt vector (NMI)
0x004 PORTC_INT_base Port C interrupt base
0x008 PORTR_INT_base Port R interrupt base
0x00C DMA_INT_base DMA controller interrupt base
0x014 RTC_INT_base Real time counter interrupt base
0x018 TWIC_INT_base Two-Wire Interface on Port C interrupt base
0x01C TCC0_INT_base Timer/counter 0 on port C interrupt base
0x028 TCC1_INT_base Timer/counter 1 on port C interrupt base
0x030 SPIC_INT_vect SPI on port C interrupt vector
0x032 USARTC0_INT_base USART 0 on port C interrupt base
0x038 USARTC1_INT_base USART 1 on port C interrupt base
0x03E AES_INT_vect AES interrupt vector
0x040 NVM_INT_base Nonvolatile Memory interrupt base
0x044 PORTB_INT_base Port B interrupt base
0x056 PORTE_INT_base Port E interrupt base
0x05A TWIE_INT_base Two-wire Interface on Port E interrupt base
0x05E TCE0_INT_base Timer/counter 0 on port E interrupt base
0x06A TCE1_INT_base Timer/counter 1 on port E interrupt base
0x074 USARTE0_INT_base USART 0 on port E interrupt base
0x080 PORTD_INT_base Port D interrupt base
0x084 PORTA_INT_base Port A interrupt base
0x088 ACA_INT_base Analog Comparator on Port A interrupt base
0x08E ADCA_INT_base Analog to Digital Converter on Port A interrupt base
0x09A TCD0_INT_base Timer/counter 0 on port D interrupt base
0x0A6 TCD1_INT_base Timer/counter 1 on port D interrupt base
0x0AE SPID_INT_vector SPI on port D interrupt vector
0x0B0 USARTD0_INT_base USART 0 on port D interrupt base
0x0B6 USARTD1_INT_base USART 1 on port D interrupt base
0x0FA USB_INT_base USB on port D interrupt base
XMEGA A4U [DATASHEET]
8387C–AVR–3/12
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15. I/O Ports
15.1 Features
• 34 general purpose input and output pins with individual configuration
• Output driver with configurable driver and pull settings:
–Totem-pole
– Wired-AND
–Wired-OR
– Bus-keeper
– Inverted I/O
• Input with synchronous and/or asynchronous sensing with interrupts and events
– Sense both edges
– Sense rising edges
– Sense falling edges
– Sense low level
• Optional pull-up and pull-down resistor on input and Wired-OR/AND configurations
• Optional slew rate control
• Asynchronous pin change sensing that can wake the device from all sleep modes
• Two port interrupts with pin masking per I/O port
• Efficient and safe access to port pins
– Hardware read-modify-write through dedicated toggle/clear/set registers
– Configuration of multiple pins in a single operation
– Mapping of port registers into bit-accessible I/O memory space
• Peripheral clocks output on port pin
• Real-time counter clock output to port pin
• Event channels can be output on port pin
• Remapping of digital peripheral pin functions
– Selectable USART, SPI, and timer/counter input/output pin locations
15.2 Overview
One port consists of up to eight port pins: pin 0 to 7. Each port pin can be configured as input or output with configurable
driver and pull settings. They also implement synchronous and asynchronous input sensing with interrupts and events for
selectable pin change conditions. Asynchronous pin-change sensing means that a pin change can wake the device from
all sleep modes, included the modes where no clocks are running.
All functions are individual and configurable per pin, but several pins can be configured in a single operation. The pins
have hardware read-modify-write (RMW) functionality for safe and correct change of drive value and/or pull resistor
configuration. The direction of one port pin can be changed without unintentionally changing the direction of any other
pin.
The port pin configuration also controls input and output selection of other device functions. It is possible to have both the
peripheral clock and the real-time clock output to a port pin, and available for external use. The same applies to events
from the event system that can be used to synchronize and control external functions. Other digital peripherals, such as
USART, SPI, and timer/counters, can be remapped to selectable pin locations in order to optimize pin-out versus
application needs.
The notation of the ports are PORTA, PORTB, PORTC, PORTD, PORTE, and PORTR.
15.3 Output Driver
All port pins (Pn) have programmable output configuration. The port pins also have configurable slew rate limitation to
reduce electromagnetic emission.
XMEGA A4U [DATASHEET]
8387C–AVR–3/12
30
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