1 Computer Organization Wireless & Mobile Networks Lab Li-hua Dong

2 Structural decomposition

3 Programming and Architectural Level Programming level –AC ←AC+[ α ] Architectural level SAR ← α SAR: Store address register SDR ←M[SAR] SDR: Store data register AC ←AC+SDR AC and SDR are both “ gated ”

4 Digital logic level The main storage and addresses in the SAR, responding to the “read” signal,and transferring the result to the SDR Switching circuits for moving the SDR and AC contents to the addr,and the sum to the AC The adder logic Timing and switching circuits for initiating each sub operation in the correct sequence

5 Application Overlap Computer architect or designer Logical designer or “clip” designer Electronics engineer contributes at Overlap between architect and logical designer and dividing line

6 Do you know The reasons for selecting binary electrical signals, rather than say ternary,octal, or decimal signals ? Inexpensive, reliable, and fast devices can be constructed that store, transfer, and perform logical operations on such signals.

7 Chapter 4 Electronic Circuits Show some of the components and circuits that produce, store,and manipulate binary electrical signals and that constitute the basic building blocks of computers. Three aspects : –Logic Gates –Bit Storage –Clocks

8 4.1 Logic Gates Electronic circuits are composed of two elements: –Passive –Active How to use to implement logic gates and bit storage

9 Operation of transistors Figure 4-1 npn Transistor

10 Not gate

11 Nor gate Figure 4-3 : nor Gate

Bit Storage Computer must store information as well as process it. electronic magnetic electromechanical memory devices Flip Flop

13 Exhibit the flip flop Figure 4-4 : Simple Flip Flop State “1” : Q=1 and Q’=0 State “0” : Q=0 and Q’=1

14 The behavior of Flip Flop Table 4.1 : The State Transition of Simple Flip-Flop

15 A simple version of Flip Flop Current State QInput DNew State Q X00 X11

16 A simple version of Flip Flop If C then Q:=D

17 A simple version of Flip Flop Pictorial symbol draw

18 The description of Flip Flop Fast and change state in nanoseconds. Complex because of the need to isolate inputs from their outputs and still permit logical feedback paths from FF output lines to their inputs.

19 Magnetic cores Ferromagnetic “donuts” that can be magnetized in either a clockwise or counterclockwise direction. Memories are built by threading a matrix of wires through the cores. Reading is accomplished by writing,and is a “destructive” read and the previous state must be restored.

20 MOS semiconductor Contains a capacitor and a transistor A binary digit is stored as an electric charge on the capacitor Zero charge may denote a binary “0” while a small charge might represent “1” Capacitor is connected to the rest of the system through the transistor which acts as a switch MOS: Metal Oxided Semiconductor and denotes A particular semiconductor technology.

21 Dynamic and static Dynamic memories ( MOS memories ) : because they Must be constantly regenerated due to –a destructive read –Leakage of the capacitor charge Static memories :Do not require regeneration mechanisms

Clocks A clock device is an electronic oscillator that produces a continuous train of digital signals at a fixed frequency Signals from a master clock are distributed throughout a computer system so that all activities may be synchronized

23 Such as “D Flip Flop” Designed internally to be sensitive to the rising or falling edge of a control or clock pulse. This permits a more precise synchronization ensure that one state change can occur per clock cycle. Expanded internally so that it is edge triggered by signal on C input. At last,the processing and memory functions of computers are implemented mainly from logic gates and storage cells, controlled by clock signals.

24 Thank you