- Fetching a workd from memory
Move (R1),R2
- Steps
- MAR <- [R1]
- Start read operation on the mem bus
- Wait for the MFC response from the meory
- Load MDR from the memory bus
- R2 <- [MDR]
- Storing a word in memory
- Address is loaded into MAR
- Data to be written loaded into MDR
- Write command is issued
Move R2,(R1)
- Steps
- R1 out, MARin
- R2out, MDRin, write MDRE === external
- MDR out, WMFC, end Wait MFC
Add (R3),R1
- Fetch the instru
- Fetch the first operand
- Perform the additoni
- Loadd the result into R1
- PC points to the first instruction,
set PC out, MAR in, Read request to memory Î