StopWatch

The next natural task would be a Stopwatch with Lap-time (mellemtid på dansk) - Please try my solution and make your own adjustment if you like. For instance could "Hours" be included in the time as well - but this call for some adjustment at the Display driver in order to select between Hours: Minutes: Seconds.

A more advanced (and harder task) could be a combined Watch + Stopwatch with the ability to set the Time of the Watch.

If you try to solve this problem with ONE HUGE State Machine are you bound to fail - (Don't even try) - However could the control-part of the watch be formed with a State Machine (An exercise to come)

Instead must you try to decompose the Problem into natural elements which each solves a part of the problem and are able to interact with each others.

The Schematic of my solution shown beneath and could act as inspiration.

My solution can be downloaded and tested at the BASYS board: Stopwatch.bit
- [Btn0] = Start/Stop - Will control the Stopwatch.
- [Btn1] = Lap time - Will show the time until pressed again (Stopwatch runs in the background or can be stopped).
- [Btn3] = Clear - Will only clear the Stopwatch when stopped.

The VHDL source code for Muxdisplay_ver3 can be found here: Muxdisplay_ver3.vhd

The Toggle_Button3 a State Machine which controlled by the "Button" input and removes eventually bouncing from the contact with a 4-bit shiftregister (not part of the State Machine).

The six internal states produces three outputs:
      Toggle: Changes state for each press of the button.
      Deboun: Will be "1" when the button pressed or else "0" (Debouched button)
      Pulse:      Like Deboun but will only be "1" for one Clk period after a press.

In order to use the 1 kHz frequency from the MuxDisplay and produce a 4-bit Bcd output with 1/10 of second resolution will this be a good component to have.

The "En" input controls the counter and Clear works asynchronous (hence the name). Rco will be "1" when the counter reaches 999 and En='1'

As the En input only will be high for one Clock pulse each second will this counter accumulate the Second-part of the time.

The same component used for the Minutes-part as well.

Rco will be "1" when the counter reaches 59 and En='1' otherwise "0"

This component produces a "Running light" at the leds in order to present the 1/10 of seconds.

Consider if this functionality should be placed elsewhere in the diagram.

In order to "freeze" the display for presentation of a Lap-time will the best solution properly be a x-bit Latch which allows the time-data to pass by under normal condition and hold the display each time the Latch high.

Just as an extra feature would it be nice to have the display-dots perform some kind of blinking in order to indicate the different states of the Watch.