Inputs left floating at the very start

Tomás Ó hÉilidhe · 2008-05-03T12:37:16+00:00

In college, I was always told not to leave input pins floating on adevice such as a 74HCT chip. I was told that the device might behaveerratically if any of its inputs are floating.I have the PIC16F684. One of its inputs goes to the data input of ashift register, and the other goes to the clock input of the sameshift register.On the shift regsiter, there's an RC circuit on the master reset witha charge time of about a microsecond (which is plenty slow enough tohave it set to all zeroes initially).When the PIC boots up, all of its IO pins are set as inputs initially.What I'm concerned about though is that shift register's input pinsmust be either high or low, so I'm wondering if I'll get erraticbehaviour at the very start because the pins are effectively floating?

May 03, 2008 23 Replies

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Hans-Bernhard Bröker 18 years ago

There's no need to make mission-critical mistakes to disgruntle our customers' customers, and eventually drive our customers to take their business elsewhere. Nagging glitches are perfectly capable of having that effect in a pretty expensive extra for cars.

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