Fetch-Decode-Execute Cycle (OCR A-Level Computer Science): Flashcards
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FDE Cycle definition
FDE Cycle definition
Process CPU uses to execute instructions; repeats for each instruction
Number of main stages in FDE cycle
Number of main stages in FDE cycle
Three
Three stages of FDE cycle
Three stages of FDE cycle
Fetch, Decode, Execute
Purpose of Fetch stage
Purpose of Fetch stage
Retrieves next instruction from memory
PC role in Fetch stage
PC role in Fetch stage
Holds address of next instruction in memory
MAR role in Fetch stage
MAR role in Fetch stage
Temporarily holds address of instruction
MDR role in Fetch stage
MDR role in Fetch stage
Receives instruction from memory, passes to CIR
CIR role in Fetch stage
CIR role in Fetch stage
Stores fetched instruction for decoding
Purpose of Decode stage
Purpose of Decode stage
CPU interprets instruction to determine actions required
Control Unit role in Decode
Control Unit role in Decode
Reads & decodes instruction in CIR into signals
Purpose of Execute stage
Purpose of Execute stage
Performs actions specified by decoded instruction
ALU role in Execute stage
ALU role in Execute stage
Performs arithmetic/logical operations on data in registers
Address Bus function
Address Bus function
Transmits memory addresses from MAR to main memory
Data Bus function
Data Bus function
Transfers data between memory & CPU, particularly to/from MDR
PC points to
PC points to
Address of next instruction, not data addresses