SLR 1 Flashcards
Structure and functions of the processor
What does the CU (Control Unit) do?
Co-ordinates all activities of the CPU
Directs flow of data between CPU and other devices
Accepts the next instruction, decodes it, handles its execution, then stores the resulting data back in memory or registers
Uses clock and registers
What does the PC (Program Counter) do?
Holds the address of the next instruction to be executed
At the start of each FDE cycle the address held in the PC is copied to the MAR
What does the MAR (Memory Address Register) do?
Holds the address of the memory location from data or an instruction
The data to and from memory must travel down the data bus and pass through the MDR
What does the CIR (Current Instruction Register) do?
Holds the current held instruction
The contents of the MDR are copied to the CIR if it’s an instruction
Contains the opcode and operand which make up the instruction
What does the ALU (Arithmetic Logic Unit) do?
Performs addition, subtraction, multipication and division
Allows for bit shift operations
Allows the boolean logic operations: Comparison, AND, OR, NOT, XOR
What does the ACC (Accumulator) do?
Data or control information is stored inside
Can store the results of the ALU for a period of time
What does the Address Bus do?
Carries memory addresses that identify where the data is being read or written to
What does the Data Bus do?
Carries the binary 1s and 0s that make up the actual information being transmitted around the CPU/Computer
What does the Control Bus do?
Carries command and control signals to and from every component of the CPU/Computer
What does the decode unit do?
It prepares the execution of an instruction by looking up the binary code in its table so the CPU knows what to do
What does the status register do?
Contains information about the state of the processor
Reads individual bits
What does the clock do?
The electronic unit that synchronises related components by generating pulses at a constant rate
Measured at hertz (the number of cycles per second)
The higher the clock rate, the faster the computer runs
What does the IR (Interrupt Register) do?
It is checked by the CPU to see if an interrupt is awaiting processing
What does the Cache do?
Holds commonly completed instructions
What does the opcode and operand do?
They make up an instruction
Opcode - Tells the computer what to do
Operand - Tells the computer what to do it to
