Summary of latches and flip-flops
Development of D-FF
- level-sensitive used in custom integrated circuits
- can be made with 4 switches
- edge-triggered used in programmable logic devices
- good choice for data storage register
Historically J-K FF was popular but now never used
- similar to R-S but with 1-1 being used to toggle output (complement state)
- good in days of TTL/SSI (more complex input function: D = JQ' + K'Q
- not a good choice for PALs/PLAs as it requires 2 inputs
- can always be implemented using D-FF
Preset and clear inputs are highly desirable on flip-flops
- used at start-up or to reset system to a known state