An overview of microcontroller (MCU) principles has been provided in Part 1. We now need to look at the PIC® internal hardware in more detail. We will use the 16F84A chip as a reference, despite its partial obsolescence, since it has all the essential elements found on all the current chips in the family without complicating features such as analogue inputs and serial ports. It is also currently included in the low-cost Proteus VSM Starter Kit for microcontroller circuit simulation. All members of the PIC family are based on the same core architecture, with each having a different combination of memory and peripheral features.
An essential reference is the PIC 16F84A data sheet, especially Figure 5.1, the block diagram of the internal architecture. A more complete picture is provided in the ‘PIC Mid Range Reference Manual’ (Figure 4-2), which includes all the peripheral options for the 16 series chips. For an explanation of the main blocks in the internal architecture, refer to Appendix C,
which describes how the registers, arithmetic and logic unit, multiplexer, decoder, program counter and memory work. Later, we will move on to the 16F690, which has a good range of peripherals and is used in the Microchip LPC demo board. All data sheets and reference manuals can be downloaded from www.microchip.com.