>>> Is it safe to leave a TTL input floating. It is my understanding
    >>> that they will pull high.

    Pulling a TTL input high only draws an extra 400 microamps. Pulling it
    low draws a whopping 1.6 ma.

REAL TTL will float high.  REAL TTL sinks 1.6mA into low input signals.  Do
YOU have REAL TTL?  That would be 74xx series.  Not 74LSxx, not 74HCTxx,
not a "ttl level input" to a cmos microcontroller.

BillW

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