Flip-flop Extras
Reset (set state to 0) – R
- synchronous: Dnew = R' • Dold (when next clock edge arrives)
- asynchronous: doesn't wait for clock, quick but dangerous
Preset or set (set state to 1) – S (or sometimes P)
- synchronous: Dnew = Dold + S (when next clock edge arrives)
- asynchronous: doesn't wait for clock, quick but dangerous
Both reset and preset
- Dnew = R' • Dold + S (set-dominant)
- Dnew = R' • Dold + R'S (reset-dominant)
Selective input capability (input enable or load) – LD or EN
- multiplexor at input: Dnew = LD' • Q + LD • Dold
- load may or may not override reset/set
Complementary outputs – Q and Q’
Output enable - tristate output