Digital signals are usually considered to be discrete values such as logic 1 or 0; however, the drive strength (none, weak, or strong) and unknown values of a signal may also be considered. The following table gives the integer values used for each of the nine states.  When a digital signal is plotted, the vertical-axis corresponds to these integer codes. For example, a digital signal that steps from a forcing 0 to a forcing 1 has a plot that steps from 3 to 4.

The following subpackages are available

Common - common digital gates

Ideal Gates - standard logic gates with no delays

Gates with Delay - standard logic gates with delays

Delay Components - components that delay a signal

Converters - converters between 2-valued and 9-valued logic

Registers - edge-triggered flip-flops and level-sensitive latches

Sources - digital sources

Tristates - transfer-gates and Wired X