A 119 KB PDF tagged as a schematic and named 27256b, the b suffix suggesting a revised variant of a 27256 part. No brand, board or device is given, so open the document to confirm its exact subject. The number pattern matches the 27-series parallel EPROM naming, where such sheets list pinout, programming algorithm and access times. When reading or burning an old firmware chip, compare the full marking and suffix on the IC with the document, since revisions can differ in programming voltage.
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 @cyberlanelectonik. 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.