Specifications

Chapter 2 - Microcontroller PIC16F84
microcontroller. It coordinates the work of other blocks and executes the user program.
CISC, RISC
It has already been said that PIC16F84 has a RISC architecture. This term is often found in
computer literature, and it needs to be explained here in more detail. Harvard architecture is a
newer concept than von-Neumann's. It rose out of the need to speed up the work of a
microcontroller. In Harvard architecture, data bus and address bus are separate. Thus a greater
flow of data is possible through the central processing unit, and of course, a greater speed of
work. Separating a program from data memory makes it further possible for instructions not to
have to be 8-bit words. PIC16F84 uses 14 bits for instructions which allows for all instructions to
be one word instructions. It is also typical for Harvard architecture to have fewer instructions than
von-Neumann's, and to have instructions usually executed in one cycle.
Microcontrollers with Harvard architecture are also called "RISC microcontrollers". RISC stands for
Reduced Instruction Set Computer. Microcontrollers with von-Neumann's architecture are called
'CISC microcontrollers'. Title CISC stands for Complex Instruction Set Computer.
Since PIC16F84 is a RISC microcontroller, that means that it has a reduced set of instructions,
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