SLR1-1.1: Fetch- Decode - Execute Cycle Flashcards
(15 cards)
What is a computer?
An electronic device that takes input, processes data and delivers an output
What is a program?
A set of instructions that a computer follows
What does the Program Counter (PC) do during the fetch stage?
• Holds the address of the next instruction
• Sends this address to the MAR
What does the Memory Address Register (MAR) do during the fetch stage?
• Receives the address from the PC
• Sends the address to memory via the Address Bus
What does the Memory Data Register (MDR) do during the fetch stage?
• Receives the instruction from memory via the Data Bus
• Sends the instruction to the CIR
What does the Current Instruction Register (CIR) do after fetch?
• Stores the fetched instruction
• Splits it into opcode and operand
What happens to the Program Counter (PC) after fetching an instruction?
• It is incremented to point to the next instruction
• If it’s a jump instruction, it’s updated with the operand from CIR
What does the CIR do during the decode stage?
• Decodes the instruction into opcode and operand
What happens if the instruction is a jump?
• The operand from the CIR is copied to the PC
• This changes the flow of the program
What happens during arithmetic or logic operations in the execute stage?
• ALU performs the operation
• ACC is used to store the result
What happens when reading data from memory?
• MAR holds the address
• MDR gets the data
• ACC stores the data
What happens when writing data to memory?
• ACC sends data to MDR
• MAR holds the address
• Data is written from MDR to memory
What role does the Address Bus play in the FDE cycle?
• Transfers addresses from MAR to memory
What role does the Data Bus play in the FDE cycle?
• Transfers data between memory and MDR
What role does the Control Bus play in the FDE cycle?
• Sends control signals from the Control Unit to coordinate operations
