Datasheet

 2018 Microchip Technology Inc. Data Sheet Complete DS40002059A-page 19
ATxmega32E5/16E5/8E5
corresponding peripheral registers from software. For details on calibration conditions, refer to “Electrical Characteristics”
on page 78.
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 8-1.
The production signature row cannot be written or erased, but it can be read from application software and external
programmers.
Table 8-1. Device ID Bytes for AVR XMEGA E5 Devices
8.3.5 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 com-
mands that erase the flash, and requires a dedicated erase command. This ensures parameter storage during multiple
program/erase operations and on-chip debug sessions.
8.4 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, etc.
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 un-programmed 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.
Device Device ID bytes
Byte 2 Byte 1 Byte 0
ATxmega32E5 4C 95 1E
ATxmega16E5 45 94 1E
ATxmega8E5 41 93 1E