Flashcards
Fetch Excecute cycle 4.7
Cards in this deck (10)
- 1Fetch-Execute CycleThe role of the CPU is to fetch and execute instructions from memory.
Instructions are fetched one at a time from main memory, decoded and executed - 2RegistersInside the processor are several registers. These are banks of switches which can store a binary value.
Many of them are general purpose registers which can be used for whatever the processor needs, but a few have very specific purposes. - 3Program counter (pc)The program counter (PC) Contains the address of the next instruction to be fetched
- 4The memory address register (MAR)The memory address register (MAR) contains the currently addressed memory location
- 5The memory buffer register (MBR)The memory buffer register (MBR) holds the code read from the currently addressed memory location
- 6The current instruction register (CIR) holds the most recently fetched machine code instructionThe current instruction register (CIR) holds the most recently fetched machine code instruction
- 7Fetch Phase 1The address of the next instruction to be executed, held in the PC, is copied to the MAR
- 8fetch Phase 2The instruction held at that address is placed in the MBR
- 9fetch Phase 3Simultaneously, the contents of the PC are incremented by 1 to get ready for the next instruction
- 10fetch Phase 4The contents of the MBR are copied to the CIR. This frees up the MBR for the execute phase
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- Flashcards on Fetch Excecute cycle 4.7, created by Ed Allen on 16/12/2019.
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- Ed Allen
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