ST7066 datasheet, a 318 KB PDF for the Sitronix dot-matrix character LCD controller and driver, commonly found on 16x2 and similar text modules and known as HD44780 compatible. It explains the instruction set, 4-bit and 8-bit bus modes, initialisation sequence, character generator and pinout. Useful when a character display shows only blocks or nothing, to verify contrast voltage, enable timing and init commands. Confirm the controller on the module is the ST7066 before following the timing tables.
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 @acodis_lcd_datasheets_EDID. 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.