logic levels Definition

The input and output logic levels, sometimes known as logic values, of nodes and groups are defined with the following characters:

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Character	Logic Level
`0`	Forcing Low (`GND`)
`1`	Forcing High (`VCC`)
`X`	Don't Care
`Z`	High impedance (no input to pin), for example, used for the "output" part of a bidirectional pin when the "input" part of the pin is driving in
`0` to `9`, `A` to `F`	Used for groups and interpreted as binary, decimal, hexadecimal, or octal values according to the current radix. The MSB is first; the LSB is last.
`DC`	Don't Care, unavailable for groups or state machine waveforms
`U`	Uninitialized
`H`	Weak High, unavailable for groups or state machine waveforms
`L`	Weak Low, unavailable for groups or state machine waveforms
`W`	Weak Unknown, unavailable for groups or state machine waveforms