In this topic we introduce the pic16F84 mcu

The PIC16F84 Microcontroller Part 1
In this topic we introduce the PIC16F84 MCU, which we will use as our baseline exemplar for the rest of the text. Here we will primarily look at internal structure, reserving external interfacing considerations for Part 3 of the topic.
After reading this topic you should:
• Recognize the difference between a microprocessor and microcontroller.
• Understand the Harvard-based architecture with its parallel fetch and execute units.
• Appreciate the function, structure and memory map of the unrelated Program and Data stores.
• Be able to interpret the Status register bits that control memory paging and hold the C, DC and Z flags.
• Know how to manipulate the contents of the Program Counter in conjunction with the PCLATH special-purpose file register.
• Understand the interaction between the clock phases and the internal sequence of micro-operations.
• Appreciates the principle of banking in the Data store and its relationship to the RP0 control bit in the Status register.
• Know what peripheral functions are integral to the PIC16F84.
What exactly is a microcontroller unit? In a nutshell, a microcontroller is a MicroProcessor Unit (MPU) which is integrated with memory and input/output peripheral interface functions on the (usually) one integrated circuit. In essence it is a MPU with on-board system support circuitry. Thus we begin by investigating the origins of the MPU. From a historical perspective the story begins in 1968 when Robert Noyce (one of the inventors of the integrated circuit), Gordon Moore1 and Andrew Grove left the Fairchild Corporation and founded their own company, which they called Intel.2 Within three years, Intel had developed all the basic types of semiconductor memories used today – dynamic and static RAMs and EPROMs.
As a sideline Intel also designed large-scale integrated circuits to customers’ specifications. In 1970 they were approached by the Nippon Calculating Machine Corporation, and asked to manufacture a suitable chip set for a line of calculators to be named Busicom. At that time calculators were a fast-evolving product and any LSI devices were likely to be superseded within a few years. This of course would reduce an LSI product’s profitability and increase its cost. Engineer Ted Hoff – reputedly while on a topless beach in Tahiti – came up with a revolutionary way to tackle this project. Why not make a simple computer central computing unit (CPU) on silicon? This could then be programmed to implement the calculator functions, and as time progressed these could be enhanced by developing this software. Besides giving the chip a longer and more profitable life, Intel were in the business of making memories – and computer-like architectures need lots of memory. Truly a brain wave. The Japanese company endorsed the Intel design for its simplicity and flexibility in late 1969, rather than the conventional implementation.