Summary datasheet for the mega16, 243 KB PDF, matching the Atmel AVR ATmega16 8-bit microcontroller; the s suffix marks the short edition. Expect the feature list, pin configurations for the available packages, a register summary and ordering information. It provides a fast way to locate power, ground, reset, crystal and ISP pins when probing a board. Full electrical tables, JTAG and programming chapters are only in the complete datasheet, which should be consulted before reflashing or replacing the part.
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.