PDF datasheet, 1.17 MB, for the Microchip PIC16C62x series of 8-bit EPROM-based microcontrollers. The document groups several family members together, so check the table of variants to see which memory size and features apply to the chip on your board. Contents normally include pin assignments, comparator and reference circuits, instruction set, configuration word and electrical characteristics. It is useful for identifying power, reset and I/O pins when probing with a multimeter or scope and for planning a replacement.
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.
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The standard format for schematics, block diagrams, power-sequence charts and service manuals.