ELEC1710 Lecture Notes - Lecture 5: Propagation Delay, Clock Signal
8 Oct 2018
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Document Summary
A latch is a type of memory device with two stable states: called a bistable logic device, 2 possible connections. Formed with cross-coupled nor or nand gates. A characteristic feature of all latches and flip-flops is. Feedback: feeding back the output into the input to hold state. Action happens when either latch is in their desired setting. If s(cid:495) low and r(cid:495) high: set the state when s(cid:495) = (cid:882) If s(cid:495) high and r(cid:495) low: reset the state when r(cid:495) = (cid:883) active- low s-r latches. Active low requires a low to be set: produces a high output, produces a low output when being reset. Output does not depend solely on the input, but also the state it was in before being set. First truth table input cannot be reliably determined as the values for the output and its conjugate are the same: the propagation delay of the gate will decide the output.
