Simulation 89 5.6. Stimulus The input applied to the design is called the stimulus. It mimics the input data signals which are applied to the design by the simulator tool. Stimulus used in your simulation provides an easy way to observe the design's behavior within and outside your design's range without damaging the hardware. Stimulus can be provided by interactively typing it in real time, a graphical testbench, or an HDL testbench. There are advantages and disadvantages to each method. You can decide which is right for you. 5.6.1. Interactive Stimulus Real-time input is typed on the command or transcript line of the simulator. The input data are not saved in a separate file. This means some information must be typed in between different simulation runs. All information is lost when the simulator is closed. This type of stimulus is not feasible for designs with a lot of inputs and, in my opinion, not feasible in most cases. Fresh out of college, I was assigned to write a design in Advanced Boolean Equation Language (ABEL). I was not very familiar with either ABEL or programmable devices. The engineer taught me to test the code manually. This meant that, at least once a day, I had to retype all the input data.