digital fundamentals 10th edition chapter 2 pdf

Example R Solution Keep in mind that S and R are only active when EN is HIGH. S Q EN Show the Q output with relation to the input signals. The gated latch has an additional input, called enable (EN) that must be HIGH in order for the latch to respond to the S and R inputs. Q Summary Latches A gated latch is a variation on the basic latch. S-R latches are frequently used for switch debounce circuits as shown: VCC Q S Position 1 to 2 Position 2 to 1 R S R Summary Latches The active-LOW S-R latch is available as the 74LS279A IC. To SET any of the latches, the S line is pulsed low. It features four internal latches with two having two S inputs. 1 0 1 Q Latch initially RESET 1 0 1 1 0 1 Q Latch initially SET Never apply an active set and reset at the same time (invalid). Q Q R Summary Latches The active-LOW S-R latch is in a stable (latched) condition when both inputs are HIGH. S R S To RESET the latch a momentary LOW is applied to the R input while S is HIGH. To SET the latch (Q = 1), a momentary LOW signal is applied to the S input while the R remains HIGH. Latch initially SET 0 1 0Īssume the latch is initially RESET (Q = 0) and the inputs are at their inactive level (1). Latch initially RESET 1 0 0 0 0 1 To RESET the latch (Q = 0), a momentary HIGH signal is applied to the R input while the S remains LOW. To SET the latch (Q = 1), a momentary HIGH signal is applied to the S input while the R remains LOW.

0 0 1 Assume the latch is initially RESET (Q = 0) and the inputs are at their inactive level (0). R R Q Q S S Q Q Summary Latches The active-HIGH S-R latch is in a stable (latched) condition when both inputs are LOW. R Q Q S NOR Active-HIGH Latch NAND Active-LOW Latch With NOR gates, the latch responds to active-HIGH inputs with NAND gates, it responds to active-LOW inputs. It can be constructed from NOR gates or NAND gates. The S-R (Set-Reset) latch is the most basic type.

Digital fundamentals 10th edition chapter 2 pdf