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Fetch-execute cycle
HC - Fetch-execute cycle
| Question | Answer |
|---|---|
| List in order the essential registers associated with the fetch-execute cycle | PC; MAR; MDR; CIR |
| What does PC stand for | program counter |
| What does MAR stand for | memory address register |
| What does MDR stand for | memory data register |
| What does CIR stand for | current instruction register |
| What is the MBR - memory buffer register also known as | MDR |
| What is the purpose of the the program counter (PC) | it holds the address of the next instruction to be fetched and executed |
| What is the purpose of the the memory address register (MAR) | it holds the address of the currently addressed memory location |
| What is the purpose of the the memory data register (MDR) | it holds the code read from the currently address memory location |
| What is the purpose of the the current instruction register (CIR) | It holds the most recently fetched machine code instruction |
| What is the typical format for a machine code instruction (what parts does it have) | Operation code (op-code); Operand |
| What is a machine code instruction | a binary code that a machine can understand and execute |
| What does the operation code (op-code) denote | the basic machine operation, e.g. add, load or store |
| What does the operand represent | a single item of binary data or the address of a single item of binary data |
| What components are used to synchronise and control the fetch-execute cycle | synchornised by the system clock and controlled by the control unit |
| How many steps does the fetch phase have | four |
| How many steps does the execute phase have | two |
| What is the register transfer notation used to describe the two steps of the execute phase: 1)The instruction held in the CIR is decoded. 2)The instruction is executed | [CIR] decoded and executed |
| What does the following register transfer notation mean: MAR <-- [PC] | The address of the next instruction to be executed, held in the PC, is copied to the MAR |
| What does the following register transfer notation mean: MBR <-- [Memory]addressed; PC <-- [PC]+ 1 | The instruction held at that address is placed in the MBR and simultaneously, the contents fo the PC are incremented by 1 to get ready for the next instruction |
| What does the following register transfer notation mean: CIR <-- [MBR] | The contents of the MBR (MDR) are copied to the CIR. This frees up the MBR for the execute phase. |
| compiled high-level languages are translated into | machine code |
Created by:
whiteauwielder
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