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buffer functions as a latch when inputs float is that normal?

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mik3ca

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I have a circuit in which I isolated a microcontroller from the outside world with tri-state buffers (74HC245). The only way I want its pins to be controlled from the outside world is if it is reset.

I have done all the circuitry and ran some tests. The logic appears valid however, it seems the 74HC245's function more like 74HC574's (flip-flops) although most of the inputs at this time are floating because they are to be connected to the PC parallel port but I'm not ready for testing from the PC as I haven't completed my circuit testing.

Is it normal for the buffer (74HC245) to function as flip-flops when the buffer inputs are mostly floating?
 

Pommie

Well-Known Member
Most Helpful Member
If your inputs are floating they will pick up any stray noise such as mains hum. Use high value pulldown resistors.

Mike.
 
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