The samples of the data input pin are shifted into a shift register first. After that the 2 most significant bits of the shift register are used to detect the current signal state (high, low) and the edge events (rising edge, falling edge). There are 4 different states/events displayed on the 7 segment display.
|rising edge||e and f|
|falling edge||b and c|
The edge events duration is extended by counters, so the events can actually be seen by the human eye.
You can test by using the dip switch connected to io_in as data input. I plan to connect a wire to the pin on the PCB by PMOD connector or custom soldering to be able to have a “measurement probe”. ;-)
|2||data input||segment c|