Buses Question And Answer.

DATA BUS correct answer - Used to transfer data between parts of the CPU and other parts of the computer. The width of the data bus is measured by the number of lines on the bus. Each line can carry one bit. A 32 bit bus can transfer 32 bits at a time. ADDRESS BUS correct answer - Holds the address of a memory location being accessed The more lines on the address bus the more locations the system can address. Maximum number of addresses = 2 width of address bus CONTROL BUS correct answer - The control bus is different from the other 2 in that it is a series of separate lines each with a different purpose which may operate at different times. READ LINE correct answer - to start a memory read once the address is on the address bus. WRITE LINE correct answer - - to start a memory write once the address is on the address bus and the data is on the data bus. CLOCK LINE correct answer - a regular pulse to time operations. A clock of 600MHz (megahertz) generates a pulse 600,000,000 times a second. RESET LINE correct answer - clear the CPU of data and fetch instructions from known location. INTERRUPT correct answer - signals from external devices e.g. printers, disk drives that require servicing. Some can be ignored. NMI correct answer - (Non Maskable Interrupts) - requests from external devices that cannot be ignored. FETCH-EXECUTE CYCLE correct answer - This describes how the processor gets instructions from memory (RAM) and carries them out. FETCH correct answer - The memory address of the next instruction from the MAR is placed on the address bus. The read line of the control bus is activated The data is placed onto the data bus and transferred to the MDR (which stores it until executed) DECODE correct answer - The control unit decodes the instruction EXECUTE correct answer - The processor carries out the instruction MEMORY WRITE OPERATION correct answer - set up the address bus with the address of the memory location by placing it in MAR set up the data bus with the data by placing it onto the MDR activate the write line on the control bus the data will now be transferred along the data bus into the correct memory location. MEMORY READ OPERATION correct answer - set up the address bus with address of the memory location to be accessed by storing in MAR activate the read line on the control bus Place the data onto the data bus and transfer along to the CPU.