Electric has a built-in gate-level simulator called ALS that can simulate schematics, IC layout, or VHDL descriptions. The simulator already knows about MOS transistors and some digital logic gates. It can be augmented with functional descriptions of any circuit using the hardware description language described later in this section.

For an example of ALS simulation, load the "samples" library and simulate the cell "tool-SimulateALS{sch}". You can load the samples library with the Load Sample Cells Library command (in menu Help).

To begin simulation of the circuit in the current window, use the ALS: Simulate This Cell command (from menu Tools / Simulation (Built-in)). After issuing this command, a waveform window will appear to control the simulation (see Section 4-11 for more). Since the ALS engine is running inside of Electric, you can place stimuli on the circuit and see the results immediately.

ALS is able to handle transistors with varying strength. To set a transistor to be weak, use the Weak command (in menu Tools / Simulation (Verilog) / Transistor Strength). To restore the strength to normal, use the Normal command. Note that this must be done before simulation begins.

#### Preferences

The Simulators Preferences (in menu File / Preferences..., "Tools" section, "Simulators" tab) has some controls that affect ALS simulation. The "Multistate display" check tells the simulator to show waveform signals with different colors to indicate different strengths. Without this, a single color is used everywhere. The other general controls at the top are discussed in Section 4-11.