Family datasheet for the Microchip PIC16F87x microcontrollers, a 3.74 MB PDF covering the flash parts in this group such as the 28- and 40-pin variants, indicated by the x. It documents pinouts, ADC, USART, MSSP, timers, the data EEPROM, configuration bits and electrical ratings. Technicians use it to find the ICSP pins, check the crystal and supply, and interpret configuration bits when reading or rewriting firmware. Confirm the exact part number on the package, since memory size and pin count differ.
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.