1. Galen SasakiEE 260 University of Hawaii1 Building D Flip Flops Combinational circuit components D Clocked Latch: similar to a flip flop but simpler D flip flop

2. Galen SasakiEE 260 University of Hawaii2 Combinational Circuit Components Voltage Inverters Normally Open Switch L H open closed Normally Closed Switch L H closed open

3. Galen SasakiEE 260 University of Hawaii3 D clocked latch DQ Clock It similar to a D flip flop but it reacts to the clock differently Q Clock DQ Clock = H =L Hold Q = D It’s “transparent” Load

4. Galen SasakiEE 260 University of Hawaii4 Differences between a D flip flop and a D clocked latch D flip flop –Triggered on positive edge of clock –Output Q (and state) changes only at a time instant D clocked latch –Output Q changes (with D) while clock is H –Output Q changes during a duration of time –Trickier to use since lots of changes can happen during a time duration

5. Galen SasakiEE 260 University of Hawaii5 Building a D clocked latch Q Hold Clock = L state stored here Load Clock = H Q D Two configurations that depend on the clock Devices drive each other

6. Galen SasakiEE 260 University of Hawaii6 Building a D clocked latch Q clock D clock = L : Hold clock = H : Load

7. Galen SasakiEE 260 University of Hawaii7 Building a D flip flop DQ Clock DQ Clock = L Load D-->Q Hold Clock = H Hold Load D-->Q

8. Galen SasakiEE 260 University of Hawaii8 Building a D flip flop DQ Clock DQ DQ DQ Hold (output doesnt change) Load (loads input) Input really doesn’t get stored until the edge Hold Load (transfers state to output)

9. Galen SasakiEE 260 University of Hawaii9 Summary Combinational circuit components –switches and voltage inverters D clocked latch –Built from switches and voltage inverters –2 configurations: load and hold D flip flop –Built from two D latches in series