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g:dffr flip flop
https://www.egr.msu.edu/classes/ece410/mason/files/lab6-supplement.pdf

g:dffr flip flop
* p24 J-K Flip Flop from Gates. Works in Simulator
https://www.egr.msu.edu/classes/ece410/salem/files/s16/lectures/Ch11_SN2.pdf
(Note: this is archived at https://web.archive.org/web/20171025113614/https://www.egr.msu.edu/classes/ece410/salem/files/s16/lectures/Ch11_SN2.pdf )

g:d flip flop with enable gate level
https://tams.informatik.uni-hamburg.de/applets/hades/webdemos/16-flipflops/20-dlatch/dff-enable.html