1919753
Fetch Execute
Cycle
- MAR <-- [PC]
- The contents of the Program
Counter are copied into the Memory
Address Register
- This is so that the next
instruction can be fetched
- This is so that the next
instruction can be fetched
- The contents of the Program
Counter are copied into the Memory
Address Register
- MBR<--[Memory]
PC <-- [PC]+1
- These two actions
happen
simultaneously
- The contents of the
Memory Address
specified in the MAR are
fetched (copied) from
memory and placed in
the Memory Buffer
Register
- The contents of the
Program Counter are
incremented so that it now
points to the address of the
NEXT instruction
- The contents of the
Memory Address
specified in the MAR are
fetched (copied) from
memory and placed in
the Memory Buffer
Register
- These two actions
happen
simultaneously
- CIR <--[MBR]
- The contents of the
Memory Buffer Register
are copied to the
Current Instruction
Register
- The contents of the
Memory Buffer Register
are copied to the
Current Instruction
Register
- [CIR] Decode
- Execute
- The OPCODE may
require data to be
fetched from
Memory into the
Accumulator
- The OPCODE may
require data to be
put into the
Accumulator from
the OPERAND
- The OPCODE may
require an operation to
be applied to the
contents of the
Accumulator
- The OPCODE may
require data to be
fetched from
Memory into the
Accumulator
- The contents of the Current
Instruction Register are now
decoded by examining the
OPCODE
- Execute
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