| Document | Section
                                            Conventions added.Peripheral
                                        sections: document structure updated.Presentation
                                        of 16-bit registers updated.Editorial
                                        updates throughout the document.
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| Pinout | Updated diagrams, legends.
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| SYSCFG - System Configuration | Content on
                                        debugging removed; see UPDI.Moved into
                                        section Memories.
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| I/O Multiplexing and Consideration | Signal names
                                        updated throughout the document.
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| AVR CPU | Invalid
                                        registers removed.
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| CLKCTRL - Clock Controller | Bit field in
                                        peripherals for clock selection is CLKSEL.CLKCTRL.XOSC32KCTRLA is under Configuration Change
                                        Protection.
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| FUSES - Configuration and User Fuses | OSCLOCK in
                                        FUSE.OSCCFG is loaded to LOCK in CLKCTRL.OSC20MCALIBB.SIGROW.TCD0CFG[7:4] - bit field names updated.
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| NVMCTRL - Nonvolatile Memory Controller | Flash
                                        sections re-organized.Command value
                                        expected within four instructions.
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| SLPCTRL- Sleep Controller | Abbreviation SLPCTRL.Behavior of
                                        peripherals in sleep modes updated.
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| CPUINT - CPU Interrupt Controller | CPUINT.LVL0PRI has no effect when Round Robin
                                        disabled.
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| EVSYS - Event System | CLKCTRL is no
                                        event user/generator.Signals
                                        EVOUT[2:0] added.
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| BOD - Brown-out Detector | Register at
                                        0x08 is BOD.VLMCTRLA.
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| TCA - 16-bit Timer/Counter | Definitions
                                        updated.TCA clock is
                                        CLK_PER.CMPnOV in
                                        TCA.CTRLC.
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| TCB- 16-bit Timer/Counter | Definitions updated.Compare/Capture register is called TCB.CCMP. 
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| TCD - 12-bit Timer/Counter | Input mode
                                        names updated.
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| RTC - Real-Time Counter | Runs in Idle
                                        sleep mode, and in Standby sleep mode if RUNSDTBY=1.RTC.CLKSEL: Bit field renamed CLKSEL.Name pattern
                                        for Busy flags in RTC.STATUS is 'xxxBUSY'.Invalid bit
                                        fields removed.
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| USART - Universal Synchronous and Asynchronous
                                Receiver and Transmitter | Clock source
                                        is CLK_PER.USART.RXDATA
                                        is read-only.RXCIF and
                                        DREIF in USART.STATUS are read-only.Interrupt RXC
                                        is shared between RXCIE and ABEIE.
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| TWI - Two-Wire Interface | Supports Fm+
                                        at 1MHz.No bridge
                                        mode supported.
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| CRCSCAN - Cyclic Redundancy Check Memory
                                Scan |  | 
| CCL - Configurable Custom Logic | LUT Control
                                        register name pattern is 'CCL.LUTnCTRLx'.Signal names
                                        updated.CCL.LUTCTRLBn: Description for INSEL1 updated.
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| ADC - Analog-to-Digital Converter | Free-running
                                        mode not available.SAMCAP=1 in
                                        ADC.CTRLC reduces sampling capacitance.Bit field at
                                        ADC.CTRLD[7:5] is INITDLY.Register at
                                        0x05 is called ADC.SAMPCTRL.Register at
                                        0x0C is called ADC.DBGCTRL.Invalid register bits removed.
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| DAC- Digital-to-Analog Converter |  | 
| AC - Analog Comparator | Inputs have
                                        name pattern 'AINxn'.Band
                                        gap-derived DAC and AC voltage reference from VREF available
                                        as input.Bit
                                        AC.CTRLA[3] is LPMODE (Low Power Mode).
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| UPDI - Unified Program and Debug Interface | Abbreviation
                                        UPDI.Invalid
                                        register bits hidden.Output Enable
                                        Timer Protection for GPIO Configuration is 8.8ms.UPDI clock
                                        adjusted by UPDICLKSEL in UPDI.ASI_CTRLA.Register
                                        Description: ranges for physical configuration registers and
                                        ASI level registers updated.CS address
                                        block notation updated.
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| Electrical Characteristics | Updated/expanded:General Operating RatingsVoltage Protection
Added:Power
                                                ConsumptionWake-Up TimePeripherals Power ConsumptionRESETOscillators and ClocksI/O
                                                Pin CharacteristicsBandgap and VREFDAC,
                                                ADC, AC
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| Typical Characteristics | Power
                                        Consumption plots updated and expanded.New sections
                                        added: GPIO, VREF, BOD, ADC, AC OSC20M, OSCULP32K.
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