ssave@ole.UUCP (Shailendra Save) (05/17/91)
I have an interesting problem: I want a logic equivalent of a flip/flop which can be configurable with a mode switch. The inputs allowed are: D and Dbar, clk and mode. When mode = 1; It should act as an edge triggered flip-flop (JK) and write on the rising edge of the clock. When mode = 0; It should act as a level sensitive latch, and write on the logic high of the clock. Minimum no. of logic gates (area) is critical as is no. of logic levels (speed). Another restraint is to use inverters and nor gates only. If you have had this problem before, or have a solution to this problem, please mail me. Thanks, Shailendra ssave@caen.engin.umich.edu
tonya@hpldsla.sid.hp.com (Tony Arnerich) (05/18/91)
One way to have selectable edge-vs.-level triggering is to use a level sensitive device, hooked up directly for level operation. For edge opera- tion, trigger through a capacitor. You might need a high value resis- tor to ground for a reset. I recall many examples like this in CMOS COOKBOOK by Don Lancaster (SAMS Books). tonya@sid.hp.com
tonya@hpldsla.sid.hp.com (Tony Arnerich) (05/22/91)
>I have an interesting problem: >I want a logic equivalent of a flip/flop which can be configurable >with a mode switch. The inputs allowed are: D and Dbar, clk and mode. >When mode = 1; It should act as an edge triggered flip-flop (JK) >and write on the rising edge of the clock. >When mode = 0; It should act as a level sensitive latch, and write >on the logic high of the clock. >Minimum no. of logic gates (area) is critical as is no. of logic levels >(speed). Another restraint is to use inverters and nor gates only. >If you have had this problem before, or have a solution to this >problem, please mail me. >Thanks, >Shailendra >ssave@caen.engin.umich.edu I have a better solution than my previous posting (which upon further thought may be more difficult than I thought at first!). Use the mode input to steer the pulses to either the CLK (toggle operation) or change the state of the Set or Reset inputs of a normal JK flipflop. This will work with one XOR gate if you only want one of Set or Reset functions. Add a couple of logic gates for full D-type flip flop operation. tonya@sid.hp.com