ATXMEGA128B1 Datasheet, PDF (12/138 Pages) ATMEL Corporation – 8/16-bit Atmel XMEGA B1 Microcontroller

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 67.
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 on page 12.
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 for XMEGA B1 devices.
Device
ATxmega64B1
ATxmega128B1
Byte 2
52
4D
Device ID bytes
Byte 1
96
97
Byte 0
1E
1E
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 (i.e., 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 and optionally memory mapped EEPROM. The data memory
is organized as one continuous memory section, see Figure 7-2 on page 13. To simplify development, I/O Memory,
EEPROM and SRAM will always have the same start addresses for all XMEGA devices.
XMEGA B1 [DATASHEET] 12
8330C–AVR–07/2012