single instruction is called its word size. Word size determines the amount of RAM that can be accessed by a microprocessor. . Data communication between CPU and memory The Central Processing Unit(CPU) has a Memory Data Register (MDR) and a Memory Address Register (MAR).
The Memory Data Register (MDR) keeps the data which is transferred between the Memory and the CPU. The Program Counter (PC) is a special register in the CPU which always keeps the address of the next instruction to be Chapter Page - - executed. The Arithmetic and Logic unit of CPU places the address of the memory to be fetched, into the Memory Address Register. A bus is a collection of wires used for communication between the internal components of a computer.
The word in the RAM has the same size (no. of bits) as the Memory Data Register (MDR). If the processor is an -bit processor like Intel , its MDR and the word in the RAM both have bits. The read operation transfers the data(bits) from word to Memory Data Register.
The write operation transfers the data(bits) from Memory Data Register to word. If 5V is applied at one end of a wire, the other end also can receive 5V. In the same way, the buses are wires, and the binary data are voltages (5V as and 0V as ), and these buses can simply pass the data as voltages from one end to other. .
Types of Microprocessors Microprocessors can be classified based on the following criteria: • The width of data that can be processed • The instruction set . . Classification of Microprocessors based on the Data Width Depending on the data width, microprocessors can process instructions. The microprocessors can be classified as follows: • -bit microprocessor • -bit microprocessor • -bit microprocessor • -bit microprocessor .
. Classification of Microprocessors based on Instruction Set The size of the instruction set is important consideration while categorizing microprocessors.There are two types of microprocessors based on their instruction sets. • Reduced Instruction Set Computers (RISC) • Complex Instruction Set