The cad/tkgate port
tkgate-2.1 – Tcl/Tk based digital circuit editor and simulator
TkGate is a graphical editor and event-driven simulator for digital
circuits with a tcl/tk-based interface. Supported circuit elements
include basic gates (AND, OR, etc.), tri-state gates, adders,
multipliers, registers, memories and mos transistors. Hierarchical
design is also supported with support for user defined modules. Save
files are based on the Verilog netlist format.