MicroController Architecture

One very common classification is on the basis of a number of instructions
1.CISC :complex Instruction Set Computers
in this controller Architecture unified memory model is used for program and data


where RAM is Data Memory and ROM is Program Memory

2.RISC : Reduced Instruction Set Computers
this Controller Architectures contains Separate Memory for Program Storage and Data Storage



A CISC processor often has many RISC like features

Another Classification is on the basis of way the Internal Data stored and manipulated inside CPU

I.Stack Machine
II.Accumulator Machine
III.Register Memory machine
IV.Register Register machines

lets take a computation of simple addition
c = A+B
In four different machines the computation is does as follows
I.Stack Machine

push A
push B
add
pop c


II.Accumulator Machine

load A
add b
store c


III.Register Memory Machine

load rx,a
add rx,b
store c


IV. Register Register Machine

load Rx,A
load Ry,b
add Rz,Rx,Ry
store c,Rz


Early Processors use either state or Accumulator(8051) modes.
Most Modern Processors use Register Register(Arduino) Architecture model.