Fetching & Executing An Instruction
Fetching involves the following steps:
a) Contents of PC are placed on address bus
b) READ signal is activated
c) Data (instruction opcode) are read from RAM and placed
on data bus
d) Opcode is latched into the CPU’s internal instruction
e) PC is incremented to prepare for the next fetch from
Execution involves decoding the opcode and
generating control signals to gate internal registers in
and out  of the ALU and to signal the ALU to
perform the specified operation.