Hitachi Semiconductor datasheet for the HA1394, a PDF of about 448 KB. The name does not describe the device function, so consult the document for the pinout, the electrical ratings, the internal block diagram and the typical application circuit. Technicians use datasheets like this to check expected pin voltages, confirm a part's role in a circuit and choose a correct replacement for a failed chip. It opens in any standard PDF reader and is worth keeping alongside the schematic of the device being repaired.
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 @datasheets0. 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.