Fetch Decode Execute Flashcards
What does the Program Counter (PC) hold?
Address of the next instruction to be fetched
What happens to the address stored in the Program Counter?
It is copied into the Memory Address Register (MAR)
How is the address sent to main memory?
Via the address bus
What signal does the control bus send to indicate the action to take?
A signal indicating what to do
What signal does the Control Unit send along the control bus?
Read signal
Where is the content from main memory sent?
To the Memory Data Register (MDR)
What is done with the contents of the MDR?
Copied into the Current Instruction Register (CIR)
What is the purpose of incrementing the Program Counter?
To point to the address of the next instruction to be fetched
What does the instruction held in the CIR get ready for?
To be decoded
What does the OPCODE indicate?
What is needed to do
What does the OPERAND specify?
What to do it to
What could the OPERAND contain?
- Actual data
- Address where data is
What is sent down the address bus to main memory?
The address
What does the Control Unit send through the control bus?
Signals for memory actions
Where are contents stored in memory sent after being signaled?
To the Memory Data Register (MDR)
What happens to the contents of the MDR after being received?
Copied to the accumulator
