# A Guide To PIC Microcontroller Documentation/Section 3 - Term-based guide to documentation
## Section 3 - Term-based guide to documentation

There are many acronyms in use in datasheets and documentation to name peripherals and features and it is not always clear what exactly is meant by them or how they relate to similar peripherals on products from other semiconductor vendors. In this section the acronyms used to describes peripherals and features on PIC microcontrollers and digital signal controllers will be listed and explained followed by the acronyms used by other semiconductor vendors. This will allow those seeking to move from other semiconductor manufacturers products to Microchip products the opportunity to quickly understand what peripheral or feature name to search for based upon their current knowledge of other devices.

### Microchip PIC MCUs and DSCs
## F
##### FSR

* FSR - File Select Register - a register in data memory used together with a INDF to implement indirect addressing. When you write software in C or some other high-level language, the compiler uses a FSR as an address register whenever you use character strings or other arrays, many other data structures, or many other abstract data types. Assembly language programmers may be familiar with what other manufacturers call an "index register" or an "address register". PIC18F parts often have 3 FSR registers (and 3 corresponding INDF registers). Recent PIC16F parts typically have 2 FSR registers (and 2 corresponding INDF registers).

## G
##### GPR

* GPR - General Purpose Register - a register in data memory with no predefined functionality. The functionality is defined by the programmer. Each GPR is, in reality, a unit of SRAM. The wording "register" is used in preference to "SRAM" to convey the idea that all SRAM in the data memory has equal standing to the WREG in that the result from an instruction can be written directly back into a GPR as the architecture does not force the result to be stored in an accumulator and then later moved from the accumulator into SRAM as would be required on some other microprocessor architectures.

## M

* MSSP - Master Synchronous Serial Port - a serial peripheral interface that can be used either as an I$^2$C, SPI or Microwire$^{TM}$ interface.

## P

* PPS - Peripheral Pin Select - a module allowing peripherals with a standard digital input or output to be connected to one of up to 30 remappable pins on the controller. Remappable peripherals include (but are not limited to) the CCP module, comparator outputs and the UARTs. Peripheral inputs and outputs which are not remappable are those which have a purely analogue functionality (A/D converter), which are complex (PMP parallel interface) or use a special I/O circuitry (I$^2$C). Remappable inputs and outputs may be connected to more than one pin simultaneously, may be connected to the same pin (to increase drive strength as an example) and an single pin could be simultaneously connected to an input from one peripheral and an output from another (allowing hardware loopback for a serial interface).

## S

* SFR - Special Function Register - a register in data memory with a defined functionality, such as the STATUS register or a register used to configure a hardware module. The opposite of a #GPR.