Presentation is loading. Please wait.

Presentation is loading. Please wait.

Latches Lecture L8.1 Section 7.1 – Book Sect. 8.1– Handout.

Similar presentations


Presentation on theme: "Latches Lecture L8.1 Section 7.1 – Book Sect. 8.1– Handout."— Presentation transcript:

1 Latches Lecture L8.1 Section 7.1 – Book Sect. 8.1– Handout

2 Sequential Logic Combinational Logic –Output depends only on current input Sequential Logic –Output depends not only on current input but also on past input values –Need some type of memory to remember the past input values

3 Cross-coupled Inverters State 1 State 2

4 !S-!R Latch !S !R Q !Q 0 0 1 1 0 1 !S !R Q !Q 1 1 0 1 0 1 0 0 1 0 1 1 1 0 1 1 1 0 X Y nand

5 !S-!R Latch !S !R Q !Q 0 0 1 1 0 1 !S !R Q !Q 0 1 0 1 0 1 0 0 1 0 1 1 1 0 1 1 1 0 X Y nand

6 !S-!R Latch !S !R Q !Q 0 0 1 1 0 1 !S !R Q !Q 0 1 1 1 0 1 0 0 1 0 1 1 1 0 1 1 1 0 X Y nand

7 !S-!R Latch !S !R Q !Q 0 0 1 1 0 1 !S !R Q !Q 0 1 1 0 0 1 0 0 1 0 1 1 1 0 1 1 1 0 X Y nand 1 0 Set

8 !S-!R Latch !S !R Q !Q 0 0 1 1 0 1 !S !R Q !Q 1 1 1 0 0 1 0 0 1 0 1 1 1 0 1 1 1 0 X Y nand 1 0 Set 1 0 Store

9 !S-!R Latch !S !R Q !Q 0 0 1 1 0 1 !S !R Q !Q 1 0 1 0 0 1 0 0 1 0 1 1 1 0 1 1 1 0 X Y nand 1 0 Set 1 0 Store

10 !S-!R Latch !S !R Q !Q 0 0 1 1 0 1 !S !R Q !Q 1 0 1 1 0 1 0 0 1 0 1 1 1 0 1 1 1 0 X Y nand 1 0 Set 1 0 Store

11 !S-!R Latch !S !R Q !Q 0 0 1 1 0 1 !S !R Q !Q 1 0 0 1 0 1 0 0 1 0 1 1 1 0 1 1 1 0 X Y nand 1 0 Set 1 0 Store 0 1 Reset

12 !S-!R Latch !S !R Q !Q 0 0 1 1 0 1 !S !R Q !Q 1 1 0 1 0 1 0 0 1 0 1 1 1 0 1 1 1 0 X Y nand 1 0 Set 1 0 Store 0 1 Reset

13 !S-!R Latch !S !R Q !Q 0 0 1 1 0 1 !S !R Q !Q 0 0 1 1 0 1 0 0 1 0 1 1 1 0 1 1 1 0 X Y nand 1 0 Set 1 0 Store 0 1 Reset 1 1 Disallowed Q 0 !Q 0

14 !S-!R Latch !S !R Q !Q 0 0 1 1 0 1 !S !R Q !Q 1 1 0 1 0 1 0 0 1 0 1 1 1 0 1 1 1 0 X Y nand 1 0 Set 1 0 Store 0 1 Reset 1 1 Disallowed Q 0 !Q 0 To close or lock with or as if with a latch, To catch or fasten

15 S-R Latch !S !R Q !Q S R CLK S R CLK !S !R Q !Q 0 0 1 1 1 Q 0 !Q 0 Store 0 1 1 1 0 0 1 Reset 1 0 1 0 1 1 0 Set 1 1 1 0 0 1 1 Disallowed X X 0 1 1 Q 0 !Q 0 Store

16 D Latch Q !Q CLK D !S !R S R S R CLK Q !Q 0 0 1 Q 0 !Q 0 Store 0 1 1 0 1 Reset 1 0 1 1 0 Set 1 1 1 1 1 Disallowed X X 0 Q 0 !Q 0 Store 0 1 1 1 1 0 X 0 Q 0 !Q 0 D CLK Q !Q

17 D Latch Q !Q CLK D !S !R S R 0 1 1 1 1 0 X 0 Q 0 !Q 0 D CLK Q !Q Note that Q follows D when the clock in high, and is latched when the clock goes to zero.


Download ppt "Latches Lecture L8.1 Section 7.1 – Book Sect. 8.1– Handout."

Similar presentations


Ads by Google