Datasheet for the legacy ATmega163 AVR microcontroller, a 2.15 MB PDF file. It documents the pin layout, memory organisation, timers, ADC, serial interfaces, programming methods and electrical ratings. It is useful when repairing older devices built on this chip, for checking supply rails, crystal and reset circuits or preparing a programmer to read and rewrite flash. Since the part is obsolete, the document also helps judge whether a newer AVR is a suitable pin-compatible replacement.
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.