Condensed summary datasheet for the ATmega64 AVR microcontroller, a 211 KB PDF. The short version usually contains the feature overview, pinout for the available packages, pin descriptions and ordering and packaging information. It serves well for fast pin identification when probing a board or verifying that a replacement part matches the original package. Full register descriptions, fuse tables and detailed electrical characteristics are not included, so pair it with the full ATmega64 datasheet for programming work.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @datasheet. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.