Discussion
Which of these correctly describes a tri-state buffer?
Answer: A
Correct answer: Its output can be logic 0, logic 1, or a high-impedance state
A tri-state buffer has an ordinary data input, an output, and an enable control. When enabled it passes the input through; when disabled its output enters a high-impedance state, effectively disconnecting it from the wire. That third state is not a logic level. It is the electrical condition of being neither driving high nor driving low, and it is what makes shared buses possible. Many devices can be wired to the same set of conductors provided that only one is enabled at a time; the rest float and do not interfere. Without it, two outputs driving the same line at opposite levels would create a short circuit from supply to ground - called bus contention - which wastes power and can damage the devices. The high-impedance state is written Z in truth tables and simulation. The alternative arrangement for a shared line is the open-collector or open-drain output with a pull-up resistor.
Post your comment
Please log in or register to post a comment.
Examination Categories
- SSC Exams
- Banking Exams
- Teaching Exams
- Civil Services Exams
- Railways Exams
- Engineering Recruitment Exams
- Defence Exams
- State Government Exams
- Police Exams
- Insurance Exams
- Nursing Exams
- Other Government Exams
- NRA CET
- PG Entrance Exams
- Campus Placement
- MBA Entrance Exams
- CUET and UG Entrance
- Judiciary Exams
- Regulatory Body Exams
- Software Development