Digital interfacing 1 Flashcards
What does Vil mean?
Vil is the maximum voltage that will be interpreted as a logic low
What does Vol mean?
Vol is the maximum voltage that will be outputted as a logic low
What does Vih mean?
Vih means the minimum voltage that will be interpreted as a logic high
What does Voh mean?
Minimum voltage outputted as logic high
What defines noise immunity?
The difference between input and output levels for logic devices
What is a propagation delay for logic devices?
The delay between input and output
When do race conditions apply?
When the inputs to a logic circuit are applied at slightly different times.
What does Current input low specify?
Current that will be sourced from an input when it is held low at Vil
What does current input high specify?
Current that will sink into an input when it is held high at Vih
What does current output low specify?
max current that can sink into an output held low
What does current output high specify?
max current sourced from an output held high
What is the fan out limit?
IoL and Ioh determine limit of inputs to single output whilst maintaining correct output voltage levels
Digital input/output circuits can be loosely divided into three categories. What are these?
Input only
Output only
Bi-directional
Output circuits can be sub-divided into 3 categories. What are these?
Push-pull (totem-pole)
open collector/open-drain
tri-state outputs
What is a pro and con of push-pull (totem-pole) system?
Its fast and can also sink or source current.
However, its outputs cannot be connected into one shared data bus
