Reference no: EM133680178

Assignment - Digital Stopwatch

For this assignment, you are going to implement the functionality for a simple stopwatch interface as shown above. The interface itself is already provided as a Logisim file named main.circ .

Your assignment must be built using this file as the interface. Failure to do so will result in no marks for Completeness of Solution

You are encouraged to use multiple circuits to implement specific components however your whole circuit must be operable and displayed using the buttons and display components in this file. That is, your solution should not require any additional interface components (e.g., buttons, displays, pins etc) in order to test the functionality of your circuit.

Logisim Version
Your assignment must be implemented using Logisim Evolution 3.8.0, which can be downloaded

This is the version we will test with, and we will not be using any other version, or making special accommodations. If your solution is incompatible with ours, it will not be able to be tested and thus will be ineligible for most marks on offer.

You can verify that your version is correct by loading the provided main.circ file with the interface as shown above.
Allowable Logisim Components
Only the following components may be used to develop your solution:
Logic Gates: any
Flip Flops: JK, D, S-R, T
LEDs
Clock (only one)
Hex Digit Display (already provided in interface)
Buttons (already provided in interface)

Pins (for connecting circuits)
Constants (for setting inputs that will not change)
Splitter (everywhere, please)
The use of any other components will be penalised - in particular, you must not use any pre-built circuits such as registers, shift registers, etc).

Implementation Stages
To break the problem down, you will implement the functionality of the stopwatch in stages. Each stage has a percentage weighting of marks contributing to the overall total of 100% You should implement each stage in order, and upon completion of each stage, save your file using the naming convention: stageX.circ.
This assignment will take a long time to complete in full. You should start early and work methodically through each stage. Note however that a good mark for this assignment does not require all stages being complete. In particular, Stages 5 and 6 are considered more advanced,

Stage 1: Implement the Start/Stop button
Using the Start/Stop button provided in main.circ, wire up a simple circuit that toggles between the
Start and Stop states every time the button is clicked. Your solution should:
Use the "Clock Started" LED and ensure it is turned on when the Stopwatch is in the Start state, and off when in the Stop state,
Make use of a Flip Flop to keep track of the current state.

Stage 2: Implement a single digit "Seconds" display
This stopwatch will provide 1 second precision, and so needs to display the number of seconds that have elapsed since the Start button was pressed. As such, this will require the implementation of a counter. You will start by implementing a single digit "Seconds" counter for the units column of the "Seconds" display. That is, a counter that increments the "Seconds" display by 1s every clock tick, between "0" and "9". Specifically:
Replace your flashing LED in Stage 1 with a counter that keeps track of the number of
"seconds" (in increments of 1s, between 0s and 9s).
The "Seconds" display should start from "00" when the Start/Stop button is first pressed
The "Seconds" display should Stop when the Start/Stop button is pressed in the Start state.
The "Seconds" display should resume counting when the Start/Stop button is pressed in the Stop state
Your circuit should explicitly ensure no illegal values are displayed (e.g., no hex values displayed)
For this stage you can assume a single clock pulse equals 1s, and the display will only show the units column in seconds. As such, your "Seconds" display should only show values: "00, 01, 02, 03, 04, 05 ...09", and then wrap back to "00".

Stage 3: Implement the full two-digit "Seconds" display
You're now going to implement full "Seconds" display for your stopwatch. Modify your circuit so that:

the seconds display now shows "Seconds" in 1s increments using both the units and tens column. That is, the display will now show values: "00, 01, 02 .... 57, 58, 59", and then wrap
back to "00".
the display resets to all zeros whenever the Reset button is clicked, and enters the Stop state (i.e., the Elapsed Time remains 00:00).
Your circuit should explicitly ensure no illegal values are displayed (e.g., no hex values displayed or digits above "5" in the tens column, etc).

Stage 4: Implement the "Minutes" display
In this stage you will implement the remaining time display components (i.e., "Minutes"). These are described in two sub-stages below. Implement a "Minutes" display using the two hex digit displays labelled "Minutes". Specifically, your "Minutes" display should:
display decimal values only from "00:00" to "99:59", and then wrap back to "00:00" (no hex values should appear)
only increment when the "Seconds" display is wrapping back to "00" (and this should be at the same time).
ensure the Start/Stop and Reset buttons work for the "Minutes" display as they do for the
"Seconds" display.

Stage 5: Implement the "Split" button
Most stop watches provide a "Split" button that allows intermediate times (i.e., lap times) to be recorded and displayed. In this stage you will implement the "Split" display. For this you will use the second "Split Time" display as shown on the Interface above to show the stopwatch time at the time the "Split" button is pressed.
Specifically, your circuit should:
display the elapsed time on the "Split Time" display at the moment when the "Split" button is
pressed, and only when the stopwatch is not in the Stop state
Ensure the displayed "Split" time remains displayed and unchanged until the next time "Split" is pressed, or the "Reset" button is pressed.
If the Reset button is pressed, the "Split" Time display should read "00:00"
Note that the "Split" button should not impact the "Elapsed Time" display. It should continue to
count as normal.

Stage 6: Implement multi-"Split" time recording
It is often useful to be able to see each "Split" time recorded (e.g., the time of each lap completed) upon completion of a timed activity. In this stage you will implement the logic required to record up to 5 separate "Split" times during a single timed activity.
When the stopwatch is active (i.e., not in the Stop state), your circuit should:
record the current "Split" time when the "Split" button is pressed
ensure up to the last 5 split times remain recorded (if more than 5 split times are recorded, it should forget the earliest split time to make room).

It must use Flip Flops to implement the storage.
Ensure the most recent split time is displayed on the "Split Time" display at all times
Set all recorded split times to 0 when the Reset button is pressed

Provide Hex Digit Displays to verify the contents of each time being stored (this should be separate from the main interface but obvious for markers to find).

When the stopwatch is in the Stop state (i.e., not currently timing an activity:

Ensure the most recent split time is displayed in the "Split Time" display at the moment the Stop state is entered.