So, whwt is the PIC microcontroller anyways? It is used in particular to implement Apple Desktop Bus (ADB) on the Macintosh SE and Apple IIgs. Here are some important datasheets for the particular version used for ADB, the PIC16CR54. Also, very important, there is a separate datasheet dedicated to describing the programming and verification interface to the PIC16CR54. If code protect is enabled, then you can’t dump out the program contents, otherwise you can using this interface, and can then duplicate an PIC chip.
20200905/DuckDuckGo PIC16CR54 datasheet
20200905/https://www.datasheetarchive.com/PIC16CR54-datasheet.html
20200905/https://www.microchip.com/wwwproducts/en/PIC16C54
20200905/http://ww1.microchip.com/downloads/en/DeviceDoc/30453E.pdf
20200905/DuckDuckGo PIC16C5X Programming Specification
20200905/http://ww1.microchip.com/downloads/en/DeviceDoc/30190h.pdf
But, I digress. To answer my first question, what is PIC exactly? Well, as it turns out, both PIC and AVR are made by the same company, and they have a huge overlap in the overall microcontroller architecture. I would reckon that PIC is an earlier version of AVR. As for AVR, there is a later version of it .