1.1 Processor Components

The part of the CPU that coordinates the activity of all other components

Signals that are sent along the control bus between the control unit and the other components of the computer

Consist of a series of connectors that transfer signals between internal components

Consists of three separate buses carrying control signals, addresses and data

• Memory Read • Memory write • Bus request • Bus grants • Clock

Causes data from the addressed location in RAM to be placed on the data bus

Causes data on the data bus to be written into the addressed location in RAM

Indicates that a device is requesting use of the data bus

Indicates that the CPU has granted access to the data bus

Used to synchronise operations

• Component performs arithmetic, logical and shift operations on data • Arithmetic operations, Add, Subtract, Multiply and Divide • Logical operations: AND, OR, NOT, XOR • Shift operations: Move bits to the left or right within a register

A general purpose register used to store the outputs of the ALU

• Program Counter • Current Instruction Register • Memory Address Register • Memory Data Register • Accumulator

Processors operate in defined stages that are used to cary out program instructions

Holds the memory address of the next instruction to be executed

Holds the current instruction, which is split into opcode and operand

Holds the address in memory where the processor is required to fetch or store data from or to

Temporarily holds data moving between the processor and main memory

To hold intermediate results of an instruction

Address of next instruction transferred from PC to MAR

Instruction stored in location addressed by MAR is transferred to MDR

PC incremented by 1

Instruction transferred from MDR to CIR

Instruction held in the CIR is decoded