Module 0368: Tracking changes of a circuit

• Terms:
  • Port: a port is a point of connection on a component, such as a gate, to a wire.
  • Node: a node is a collection of wires that are electrically connected.
  • Component: a component is typically a gate or a device that has input ports and output ports.
  • Propagational delay: it takes a short amount of time for a component to update its output port(s) after at least one of the input ports is changed. This amount of time is called a propagational delay.

In pseudocode, the logic can be summarized as follows:

• Begin with a starting state. This is usually signified by NC boldfaced.
  • The initial changes to the input pins are usually boldfaced on this row.
  • For the initial NC row, update ports node-connected to the ports of updated input pins.
• Perform the following steps until there is no change from the last step (PD row):
  • This is an NC (node connectivity) row. Depending on the wiring of the circuit, update all other ports of the same node connected to a port that is changed.
    • As a general rule, an NC row should only have ports corresponding to input pins changed. The port of an output pin is considered an input.
  • This is a PD (propagational delay) row. After a propagational delay, analyze and compute the output port(s) of every component with at least one input port changed in the previous NC step.
    • Only record in the table if an output port is changed from its current value.
    • As a general rule, a PD row should only have ports corresponding to the changed output pins.
    • When a PD row is empty, reflecting there is no change, then a steady state is reached.

Mechanically, this can be done by using a spreadsheet or any table.

This site is licensed under Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International 🅭🅯🄏🄎.
Improve this page by contributing and editing ,
or create an issue or participate in a discussion.
or View the source document.