Sorry, but you cannot use the term "bouncing" if you have no switches or hardware. If you have a timing issue, it is not due to what you are calling "bouncing". The correct term for what you are describing (which is not occurring is "ringing". All the TTL signals involved on your board meet TTL spec (meaning they don't have ringing) so there is no point in talking about "bouncing" . If for example you ran a TTL signal on a very long cable, you could have ringing due to reflected wave but that is not the case here. I'm not saying you don't have a timing issue, I"m just saying that and "settling time" should not come into the conversation unless your timing is off. It is standard procedure to put very small delays for managing timing issues but it is not because of any "bouncing" but because it is a good practice to do so. When you add switches and relays we can talk about switch bounce, which is a physical fact. We haven't talked about decoupling caps so maybe you have noise on your +5V power bus, which is noise , not bouncing. A negative spike could falsely trigger an interrupt which is why it is standard practice to have 0.1uF decoupling caps adjacent to all IC's running on +5V. CMOS (+12v) does not suffer from that vulnerability so it is not common to see such caps on CMOS circuits.