Datasheet for the Atmel ATxmega256A3B, a specific AVR XMEGA microcontroller with 256 KB of flash in a 64-pin package. The B suffix marks the variant with a battery backup system for a real-time counter, differing slightly from the plain A3. The 3.35 MB PDF covers pinout, electrical characteristics, package data and errata. Use it to identify the backup supply pin, PDI and JTAG programming pins and main power rails. Peripheral register details are in the XMEGA A family manual.
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