FDE Cycle Flashcards
What is the FDE cycle?
the process that processor follow in order to execute instructions
What is the fetch stage?
where the next instruction is fetched from RAM
What is the decode stage?
where the instruction is decoded by the decode unit
What is the execute stage?
where the instruction is carried out
Fetch stage
PC loads address of next instruction into the MAR
MAR sends the address along the address bus to RAM
control unit sends a READ signal to RAM via the control bus
RAM sends instructions in the memory address location onto the data bus
MDR receives instructions from data bus
MDR loads instruction into the CIR
Decode stage
CIR loads instructions into the decode unit
decide unit decodes instructions
Execute stage
depends on the code/instruction
e.g LOAD decode sends address to load to MDR and a fetch cycle begins
e.g STORE decode sends address to store in MDR to address bus ACC sends data store to MDR, data bus CU sends WRITE signal to RAM, control bus
What is opcode?
corresponds to the operation that the CPU will perform
e.g. this could be a binary string corresponding to LOAD, SUB, ADD etc
What is operand?
references the data that the operation will be performed on
this could be the data itself or it could be a memory address related to that data
