Describes a driven clock signal. For clock drivers that are not directly associated with a signal, the clockName attribute can be used to associate a name with the clock. The clockSource attribute can be used on these clocks to indicate the actual clock source (e.g. an output pin of a clock generator cell). Clock period in units defined by the units attribute. Default is nanoseconds. Time until first pulse. Units are defined by the units attribute. Default is nanoseconds. Value of signal after first clock edge. Duration of first state in cycle. Units are defined by the units attribute. Default is nanoseconds. Describes a driven one-shot signal. Time in nanoseconds until start of one-shot. Value of signal after first edge of one-shot. Duration in nanoseconds of the one shot. Specifies if a signal requires a driver. Default is false. The attribute driverType can further qualify what type of driver is required. Undefined behaviour if direction is not input or inout. Driver type any indicates that any unspecified type of driver must be connected Describes a signal value. The signal value can be just a value (number), a strength, or both. If the "value" is not given, it should be considered an X (unknown). A weak strength with no value given is considered Z (tristate). Describes a signal strength. The value of a signal. 1 or 0 for single bit signals, unsigned numeric otherwise. The strength of the signal. "strong" (default) or "weak".