ATXMEGA384C3 datasheet(13/126 Pages) ATMEL

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XMEGA C3 [DATASHEET]

8361C–AVR–4/12

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 65.

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 7-1.

The production signature row cannot be written or erased, but it can be read from application software and external

programmers.

Table 7-1.

Device ID bytes.

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, and startup configuration.

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 7-2 on page 14. To simplify

development, I/O Memory, EEPROM and SRAM will always have the same start addresses for all Atmel AVR XMEGA

devices.

Device

Device ID bytes

Byte 2

Byte 1

Byte 0

ATxmega384C3

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