Library for digital electrical components based on the VHDL standard with 9-valued logic and conversion to 2-,3-,4-valued logic

Package Contents


User's Guide


Examples that demonstrate the usage of the Digital electrical components


Basic definitions


Truth tables for all components of package Digital


Delay blocks


Basic logic blocks without delays


Logic gates including delays


Time-dependent digital signal sources


Converters between 2-,3-,4- and 9-valued logic


Registers with N-bit input data and output data


Transfergates, Buffers, Inverters, and WiredX




This information is part of the Modelica Standard Library maintained by the Modelica Association.

This library contains packages for digital electrical components. Both, type system and models are based on the VHDL standard (IEEE Std 1076-1987 VHDL, IEEE Std 1076-1993 VHDL, IEEE Std 1164 Multivalue Logic System):

  • Interfaces: Definition of signals and interfaces
  • Tables: All truth tables needed
  • Delay: Transport and inertial delay
  • Basic: Basic logic without delay
  • Gates: Basic gates composed by basic components and inertial delay
  • Tristate: (not yet available)
  • FlipFlops: D-Flip-Flops
  • Latches: D-Latches
  • TransferGates: (not yet available)
  • Multiplexers (not yet available)
  • Memory: Ram, Rom, (not yet available)
  • Sources: Time-dependent signal sources
  • Converters
  • Examples

The logic values are coded by integer values. The following code table is necessary for both setting of input and interpreting the output values.

Code Table:

Logic value Integer code Meaning
'U' 1 Uninitialized
'X' 2 Forcing Unknown
'0' 3 Forcing 0
'1' 4 Forcing 1
'Z' 5 High Impedance
'W' 6 Weak Unknown
'L' 7 Weak 0
'H' 8 Weak 1
'-' 9 Do not care

The library will be developed in two main steps. The first step contains the basic components and the gates. In the next step the more complicated devices will be added. Currently the first step of the library is implemented and released for public use.

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