Sometimes when you get to the Downloading to the Board section in labs you will be asked to hook up an input to an output, such as hooking up a switch to an input port and then hooking up that same port to an LED. You cannot do this directly. In Lab 5, you only need to use this in the top level module you make near the end of the lab.

After finishing the last Verilog module for a lab, build a new top level Verilog module that instantiates your completed lab module. The top level module should have all the same input and output names and pass these into the instantiated lab module. Also, add the inputs that need to be added as outputs along with their output counterpart. Note that this will require two separate ports for each input/output hookup.

Now you'll need to include a buffer to hook up each input and output counterpart. The following diagram shows this. How to use a buffer is explained afterwards.

The following example demonstrates how to instantiate and use a buffer.

  input switch_in;
  output switch_out;
 
  // like this
  assign switch_out = switch_in;

assign simply assigns the output that you want to use to the same value as the input that you want to use. This essentially creates a buffer. This allows you to assign a whole bus's value to another.

This allows you to use inputs as outputs to hook up things like switches to LEDs or buttons to seven segment displays!