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The Fetch – Execute Cycle. The control unit sets up the address bus by transferring the contents of the PC to the MAR. The control unit activates the READ line on the control bus and the contents of the memory location are transferred to the MDR.
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The Fetch – Execute Cycle The control unit sets up the address bus by transferring the contents of the PC to the MAR The control unit activates the READ line on the control bus and the contents of the memory location are transferred to the MDR The control unit decodes and executes the instruction The instruction is transferred to the IR in the control unit The PC is incremented
Memory Read Operation • The control unit sets up the address bus by transferring the memory address to be accessedto the MAR • The control unit activates the READ line on the control bus andthe contents of the memory location are transferred to the MDR • If necessary the contents of the MDR are transferred to the Accumulator
Memory Write Operation • The control unit sets up the address bus by transferring the memory address to be accessedto the MAR • Set up data bus by transferring data to the MDR • The control unit activates the WRITE line on the control bus and the contents of the MDR are transferred to the memory location