Latches and Flip-Flops Flashcards
Digital circuits can be classified in two categories. The difference between the two is the way that they produce outputs.
- _______ circuits produce outputs only when an input is applied. They are composed of logic gates that have no feedback from output to input. When the input is removed, the output stops. As a result, cthese circuits cannot store information.
- ________ circuits also produce an output when an input is applied, but these circuits will retain the output after the input is removed. Basically, they “remember” their last input condition.
- Combinational circuits
- Sequential circuits
The circuit below is nothing more than a single _____gate with its output tied to one input leg. The other input leg is tied to a switch. The switch is used to apply either ground or 5 volts. The line tying the output to the input is called a ______ line . The purpose of this line is to provide a path for the output of the gate to be returned to the input.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/088/373/q_image_thumb.png?1659503504)
The circuit below is nothing more than a single OR gate with its output tied to one input leg. The other input leg is tied to a switch. The switch is used to apply either ground or 5 volts. The line tying the output to the input is called a feedback line. The purpose of the feedback line is to provide a path for the output of the gate to be returned to the input.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/088/373/a_image_thumb.png?1659446775)
In a sequential circuit, the feedback line is the defining factor. It allows the gate to ________
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/088/826/q_image_thumb.png?1659503506)
In a sequential circuit, the feedback line is the defining factor. It allows the gate to “remember” its previous output.
Circuits composed of logic gates that have no feedback lines are called _______.
combinational circuits
Feedback lines are used to tie the _______.
output of a gate back to an input
A _____ changes states when its inputs are changed. A _____ can only change states when the clock pulse is changed.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/097/207/q_image_thumb.png?1659503524)
A latch changes states when its inputs are changed. A flip-flop can only change states when the clock pulse is changed.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/097/207/a_image_thumb.png?1659446793)
The basic _____ is constructed of two gates (either NOR or NAND gates or their equivalents) with the feedback lines cross-coupled between the gates.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/097/378/q_image_thumb.png?1659503526)
The basic latch is constructed of two gates (either NOR or NAND gates or their equivalents) with the feedback lines cross-coupled between the gates.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/097/378/a_image_thumb.png?1659446794)
An active-HIGH input RS latch is constructed of two _____ gates.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/097/745/q_image_thumb.png?1659503527)
An active-HIGH input RS latch is constructed of two NOR gates.
An active-LOW input RS latch (RS latch) is constructed of two _____ gates.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/097/919/q_image_thumb.png?1659503528)
An active-LOW input RS latch (RS latch) is constructed of two NAND gates.
Latches and flip-flops have two outputs, designated as Q and Q (spoken as either “_____” or “______”). Ideally, the output state of Q and Q should be opposite at all times. These opposite outputs are also known as complementary outputs.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/098/270/q_image_thumb.png?1659503528)
Latches and flip-flops have two outputs, designated as Q and Q (spoken as either “Q NOT” or “NOT Q”). Ideally, the output state of Q and Q should be opposite at all times. These opposite outputs are also known as complementary outputs.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/098/270/a_image_thumb.png?1659446796)
When a latch’s Q output is HIGH and its Q output is LOW, the latch is considered_____. This output state is also referred to as the HIGH or 1 state.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/098/792/q_image_thumb.png?1659503528)
When a latch’s Q output is HIGH and its Q output is LOW, the latch is considered SET. This output state is also referred to as the HIGH or 1 state.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/098/792/a_image_thumb.png?1659446796)
When a latch’s Q output is LOW and its Q output is HIGH, the latch is considered _____ This output state is also referred to as the LOW or 0 state.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/099/042/q_image_thumb.png?1659503529)
When a latch’s Q output is LOW and its Q output is HIGH, the latch is considered RESET. This output state is also referred to as the LOW or 0 state.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/099/042/a_image_thumb.png?1659446797)
These two output states coincide with the _____ and ______ inputs.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/099/186/q_image_thumb.png?1659503529)
These two output states coincide with the “S” (SET) and “R” (RESET) inputs.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/099/186/a_image_thumb.png?1659446798)
On the occasion that both outputs are the same, the terms most frequently used for the output condition are: “______________”.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/099/376/q_image_thumb.png?1659503530)
On the occasion that both outputs are the same, the terms most frequently used for the output condition are: “ILLEGAL”, “UNDESIRED”, and “INVALID”.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/099/376/a_image_thumb.png?1659446799)
Schematically, latches are indicated by either a _____ of the circuit (the two cross-coupled gates) or a ______ (rectangular box).
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/099/722/q_image_thumb.png?1659503530)
Schematically, latches are indicated by either a logic diagram of the circuit (the two cross-coupled gates) or a logic symbol (rectangular box).
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/099/722/a_image_thumb.png?1659446800)
The ______ is constructed of two cross-coupled NOR gates. The feedback lines extend from the output of each gate to one input leg of the opposite gate.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/129/100/642/q_image_thumb.png?1659503530)
RS latch