1.1 Flashcards
What does the ALU do?
It does arithmetic and logic operations. Simple arithmetic or < and > comparisons.
What does the control unit do?
It directs operations within the processors, lets the ALU, memory and I/O know how to respond to instructions from a program. Synchronises actions using an inbuilt clock. Controls FDE cycle.
What does the memory unit do?
It holds current data and instructions, files, and operating system that the CPU needs. A CPU must pull instructions and data from main memory into the registers. Data must be in use if not it will be stored.
What does the program counter do?
It contains the address of the instruction being executed at the current time. As each instruction is fetched, the program counter increases by 1.
What does the MAR do?
It stores the memory address from which data will be fetched for the CPU, or the address to which data will be sent and stored.
What does the MDR do?
It holds information that is in the process of being transferred from the memory to the central processor.
What does the CIR do?
It holds the instruction currently being executed or decoded.
What does the accumulator do?
It stores the results from the ALU
What is a bus request?
An indicator that a device is requesting the use of the data bus.
What is a bus grant?
An indicator that the CPU has granted access to the data bus.
What does a memory write do?
It causes data on the data bus to be written into the addressed location.
What does a memory read do?
It causes data from the addressed location to be placed on the data bus.
What is an interrupt request?
An indicator that a device is requesting access to the CPU.
What does the clock do?
Synchronises operations.
