27 Sep
2005
27 Sep
'05
5:57 p.m.
If a tristate buffer is enabled by its control line, but the input to
the buffer is at high-Z is there a typical output?
No, the input will float. _Most_ TTL buffers have inputs that should
float high (so the output will be whatever you should get for a high
input), CMOS ones will pick up random noise. A very few buffers will
float low, I think.
If you require the output to be at a known state under such condtions,
you need to ensure the input is at a known state too, e.g. by adding a
pull-up resistor.
One thing you can be sure of is that the output will not be
high-impedance if the buffer is enabled. The bit of your message that I
deleted seems to suggest you were hoping it would be.
-tony