1. Logic Design CS221 1 st Term 2009-2010 Storage (memory) Cairo University Faculty of Computers and Information

2. 24/10/2009 cs221 – sherif khattab 2 Administrivia homework #3 due Dec. 8 th in lecture Project design due Dec. 8 th in lecture course web site:  http://www.fci-cu.edu.eg/~skhattab/cs221/

3. 24/10/2009 cs221 – sherif khattab 3 multiplexers with 3-state gates 3-state gates  logic 0  logic 1  high-impedance (open)‏ 3-state buffer gate

4. 24/10/2009 cs221 – sherif khattab 4 multiplexers with 3-state gates

5. 24/10/2009 cs221 – sherif khattab 5 multiplexers with 3-state gates

6. 24/10/2009 cs221 – sherif khattab 6 storage elements storage (memory) elements store bits while power is on until input signals cause them to switch the stored bits stored n bits input signals

7. 24/10/2009 cs221 – sherif khattab 7 storage elements latches:  storage elements that operate on the levels of input signals (0 or 1)‏  level-sensitive flip-flops:  storage elements that operate on the transitions in input signals (0->1 or 1->0)‏  edge-sensitive flip-flops are more common. flip-flops are constructed from latches.

8. 24/10/2009 cs221 – sherif khattab 8 SR-latch 2 inputs: S (Set) and R (Reset)‏ 2 outputs: Q and Q' Function Table

9. 24/10/2009 cs221 – sherif khattab 9 SR-latch with enable

10. 24/10/2009 cs221 – sherif khattab 10 D latch

11. 24/10/2009 cs221 – sherif khattab 11 graphic symbols for latches

12. 24/10/2009 cs221 – sherif khattab 12 D flip-flop edge-triggered

13. 24/10/2009 cs221 – sherif khattab 13 D flip-flop