INTRODUCTION TO MICROPROCESSOR OPERATION
The microprocessor works by executing a program of instructions. Creating the program is similar in concept to programming in BASIC, C, or any other high-level computer
language. Each type of microprocessor has its own instruction set, which is the set of commands that it was designed to recognize and obey. Microprocessor instructions are very elemental and specific, and it usually takes more than one to accomplish what a single, high-level language instruction would. Many microprocessor instructions simply move data from one place to another within the computer; others perform mathematical or logic operations. Still another group of instructions control program flow, such as jumping forward or backward in the program. Each instruction in the instruction set is assigned its own unique operation code, (which is typically 8 bits long and
referred to as the op-code). The CPU uses this 8-bit number to identify the instruction. All microprocessors have at least one accumulator [Figure 4(a)], which is a dataholding register in the CPU. The accumulator acts as a “staging area” for data.