Complete 3.65 MB datasheet for the mega640, 1281, 1280, 2561 and 2560, consistent with the Atmel AVR ATmega640/1280/1281/2560/2561 family, the larger AVR parts in 64 and 100-pin packages. It should document pin functions, memory, peripherals, electrical characteristics, JTAG and ISP programming. Repair technicians use it to trace ports on dense boards, wire a programmer to the correct pins, check fuse options and confirm voltage limits. Check the chip marking to know which family member is fitted.
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.