Tri-State Buffer Control Bits Quiz

18 Questions

What is the condition for the bus to function properly in terms of the control bits c0, c1, and c2?

At most one of the control bits should be 1

What is the function of a tri-state buffer?

To control when an output signal makes it to the bus

What state does a tri-state buffer output when its control bit is inactive?

High-impedance or 'Z'

Which device is mentioned in the text as a component of output interfacing with external devices?

Flip-flop

What is the primary function of a flip-flop or latch in digital electronics systems?

To store state information

How many stable states does a flip-flop have and what can be stored in it?

Two stable states to store a binary digit

What is the behavior of a tri-state buffer when the control bit is 1?

It has high impedance/no current

How many wires are involved when implementing a multi-bit tri-state buffer with 32 wires?

64 wires

Why is a tri-state buffer commonly used in devices that communicate on a bus?

To prevent multiple devices from writing to the bus

How can a multi-bit tri-state buffer be implemented with 32 wires and only 1 control bit?

With 32 tri-state buffers, each taking one bit as input and output

What is the purpose of using a tri-state buffer in controlling bus communication?

To manage which device writes to the bus at a given time

In what scenario would multiple devices outputting data to a shared bus cause issues?

When multiple devices attempt to write to the bus simultaneously

In a multi-bit tri-state buffer, each individual bit has its own control input. What is the purpose of having separate control inputs for each bit?

To allow individual bits to be turned on or off independently, facilitating bus communication

Considering an active-low tri-state buffer, what is the state of the output when the control input is at logic 1?

The output is in a high-impedance state (Z)

How can tri-state buffers be used to implement a bidirectional data bus?

By connecting the outputs of two tri-state buffers in parallel, with their control inputs driven by separate signals

What is the primary purpose of using tri-state buffers in digital circuits?

To facilitate communication between multiple devices on a shared bus

In a system with multiple tri-state buffers connected to a common bus, how can bus contention be avoided?

By ensuring that only one tri-state buffer is enabled at a time

Consider a tri-state buffer with an active-low control input. What is the output state when both the data input and the control input are at logic 0?

The output is at logic 0

Study Notes

Buffers

A buffer is an active device that requires additional inputs to power the gate and provide voltage and current.
A tri-state buffer is a device that allows control over when current passes through it.

Tri-State Buffer

A tri-state buffer has two inputs: a data input (x) and a control input (c).
The control input acts like a valve, controlling when the output is the input.
When the control input is active, the output is the input (z = x).
When the control input is not active, the output is "Z" (high impedance/no current).

Active-High Tri-State Buffer

The output is Z (high impedance/no current) when c = 0.
The output is x when c = 1.

Active-Low Tri-State Buffer

The output is x when c = 0.
The output is Z (high impedance/no current) when c = 1.

Examples

A tri-state buffer is used to control when an output signal makes it to the bus.
When the control bit is active, the input of the device makes it to the output.
When the control bit is not active, the output of the device is Z (high impedance/no current).

Output Interfacing

Output interfacing is used to output data from the data bus to external devices connected to the controlling system.
D-flip flop is an example of an interfacing component.

D-Flip Flop

A flip-flop is a circuit that has two stable states and can be used to store state information.
Flip-flops are used as data storage elements and can store a single bit (binary digit) of data.
Flip-flops have the opposite behavior of a tri-state buffer.

Multi-Bit Tri-State Buffers

A multi-bit tri-state buffer can control many wires using a single control bit.
This can be implemented using multiple tri-state buffers taking one bit as input and one bit as output.

Why Tri-State Buffers?

Tri-state buffers are used to control what gets on the bus and what doesn't.
They prevent multiple devices from writing to the bus at the same time.
They allow multiple devices to read from the bus while preventing multiple devices from writing to it simultaneously.

Test your knowledge on how tri-state buffers operate and prevent multiple devices from writing to a bus simultaneously. Understand when the buffer's control bit is active and how it affects the output signal.

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