A Guide To PIC Microcontroller Documentation/Introduction to PIC microcontroller and DSC products
Methodology behind PIC® controller documentation
Microcontrollers and digital signal processors (DSPs) are challenging products to document. On the one hand, the semiconductor vendor has to describe the functionality of the device's processing core, the functionality and possible settings of peripherals and the electrical and packaging specifications of the device. This description needs to concentrate on the raw functionality of the device's circuitry and the registers which they form. For example, a UART (Universal Asynchronous Receiver Transmitter) peripheral's functionality, as described in a datasheet, focuses upon, among other things, setting up the related transmit and receive pins of the device for use as a serial interface, how to calculate the required baudrate settings and how to enable parity support.
On the other hand, raw details on functionality and setup alone cannot inform a developer how to use that peripheral, processor or other feature in an actual application. Using our UART example again we know that a UART can be used in a variety of serial interfacing standards such as RS-232 and RS-485 amongst others. In addition that standard may have standardised software layer with which it is commonly used (for example ANSI escape sequences used with VT100), and a common circuit layout external to the controller to implement the required signalling (for example a MAX-232 family transceiver used with RS-232).
A further challenge documenting controller products is due to their infinite flexibility, as programmable products, and the fact that the software can be written in a variety of different programming languages using a broad range of software tools from different vendors of which some, or perhaps none, come from the silicon vendor themselves.
Lastly there is the issue of the software programs and hardware tools used for creating and debugging the firmware for the controller and the programming tools used for small production runs or mass-production.
As a result, datasheets alone typically contain around 100 pages, often running to several hundred pages, and in the interest of keeping the size of the datasheet manageable, much common and implementation or application specific data is located in various other documents with names such as "Family Reference Manual", "Application Note" or "Programming Specification".