As long as input is nonzero, output should be 1.
When input is 0, even for 1 sample, output changes to 0 and stays at zero for n samples. Even if input becomes nonzero again, the output stays latched.
Any cheap simple way to do this?
Something involving a timer and feedback to keep its input from resetting until it outputs 1? something with a peak hold? (though that adds 19 MIPS)