Lab 2 Alarm Clock

Objectives
Work in Xilinx Vivado and design a simple alarm clock in Verilog. There will be two
alarms that can be set, either of which can be triggered based on the current clock
time.
Inputs/Outputs
The individual inputs and outputs of the top module alarm_clock are already
connected. You only need to code two modules, alarm_fsm and clock_fsm,
described in steps 1 & 2 below.
Inputs to the Alarm Clock
• CLK – the on board 100Mhz clock
• SW[7:0] – the eight board switches
o SW[7:2] are unused in thislab
o SW[0] enables alarm0
§ Ialarm0_fsm.alarm_en_pi
o SW[1] enables alarm1
§ Ialarm1_fsm.alarm_en_pi
• BTN[3:0] – the four board push buttons
o BTN [0] is the minute increment button. When not pressing other
button, this button will increment the clock minute value by 1 when
pressed.
§ When an alarm is being programmed, this instead increments
the alarm’s minute value by 1.
o BTN[1] is the hour increment button. When not pressing other buttons,
this button will increment the clock hour value by 1 when pressed.
§ When an alarm is being programmed, this instead increments
the alarm’s hour value by 1.
o BTN[2] displays the current setting for alarm 0, and allows alarm 0 to
be programmed with buttons 0 & 1.
o BTN[3] displays the current setting for alarm 1, and allows alarm 1 to
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be programmed with buttons 0 & 1.
Outputs of the Alarm Clock
• LED[7:0] – the eight board LEDs
o LED[5:0] will display the current clock seconds in binary. It should never
exceed 59, 6’111011.
o LED[6] is the output of alarm 0. It will blink when alarm 0 is
triggered.
o LED[7] is the output of alarm 1. It will blink when alarm 1 is
triggered.
• SEG[6:0], DP, AN[3:0] – the seven segment display
o This works exactly asit did in the previouslab, although the hours and
minutesfrom eithertheclockorthealarmbeingdisplayedarepassed
through a binary to decimal converter to display a more human
readable digital clock.
o To look more like a real world clock, there is also a modification to
make the clock ‘blink’ when it is first running, before the user has
programmed the clock
Provided files
Download lab2.v and the Nexys4DDR design constraint file from the FPGA Lab 2
Files on Canvas.
In this lab, the combinational logic to display the currently set time and currently
programmed alarms is already present in lab2.v. You will only need to implement the
two blocks of sequential logic, alarm_fsm and clock_fsm, described below.
Step 1: 12-hour Alarms
The module alarm_fsm is a module that has a set of clock inputs for minute and hour
values, and a set of minute and hour value outputs that represent the ‘programmed’
alarm time. When the input values match the programmed values and the alarm is
enabled, the module drives an ‘alarm triggered’ event that the system outputs to one
of the board LEDs.
In lab2.v, implement the alarm_fsm module, as follows:
• The outputs ofthemodule that you will need to generate logic for are:
o minutes_po – the ‘minutes’ value ofthe alarm
o hours_po – the ‘hours’ value of the alarm
o alarm_triggered_po – the alarmeventitself, truewhen the alarmtriggers
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• If the alarm is enabled (input: alarm_en_pi) and the clock input time in
minutes and hours matches the alarm minutes_po and hours_po, trigger the
alarm (output: alarm_triggered_po)
• The event alarm_triggered_po should remain high until it is cleared, i.e.
the alarm enable is driven to 0
o The alarm enables signals are mapped to switches, so this means
once an alarm goes off, you will need to flip the alarm’s switch to
disable the alarm
• Increment the alarm minutes_po and hours_po reg based on the increment
inputs
o Both values should increment whenever the increment inputs are high.
The increment inputs will be high for exactly one clock cycle whenever
the corresponding buttons are pressed
o Both values should wrap appropriately
§ Minutes_po should transition from 59-0
§ Hours_po should transition from 12-0
You should be able to test this step before you move on to Step 2. There are two
alarm_fsm modules instantiated in the alarm_clock top level module. Both should
function, using the buttons and switches as described in the inputs/ouputs section
above. Test them to make sure the alarms trigger correctly before moving on to the next
step.
Step 2: 12-hour Clock
The clock_fsm module is a simple 12-hour digital clock that continuously counts upwards.
It has seconds, minutes, and hour values stored. It also has inputs for manually
programming the minutes and hour values, similar to how the alarm_fsm module minutes
and hour values were programmed in the previous step.
In lab2.v, implement the clock_fsm module.
You wrote the alarm_fsm module first because most of the logic of the clock_fsm
module is identical to the alarm_fsm module, with one addition:
• Like the alarm_fsm module, the clock_fsm minutes_po and hours_po
outputs should increase by 1 whenever the corresponding increment input is
true.
• However,there is an additionalrule forthe clock_fsm:the clock should actively
countuponce per second.There isaclk_en_pi signal on the clock_fsmmodule.
It will beactive onecycle of clk_pi persecond.
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o The seconds_po signal should increment every second – so on the
posedgeofclk_pi, whenever clk_en_pi is true.
o Like minutes_po,seconds_po should wrap from 59 - 0.
• Whenever the seconds value wraps from 59-0, the minutes_po should
increment by one. Similarly, when the minutes_po value wraps from 59-0,
the hours_po value should increment
• Note: Like most real world digital clocks, you do not need to increment
hours_po when programming minutes_po with the buttons.
o As an example, if the clock reads “1:59” and minute passes, it
will read “2:00”. However, if it reads “1:59” and button 0 is
pressed, the clock can transition to “1:00”. Many real world
clocks that have both hour and minute programming buttons
will do this for simplicity. You can do either (“1:00” or “2:00”)
when button 0 is pressed, but the logic is far simpler if you
choose to only increment hours_po when minutes_po naturally
rolls over from 59 to 00 with the passage of a full minute.
Step 3: Simulation
After you successfully complete your implementation, download sim1.v from the
FPGA Lab 2 Files on Canvas.
Add this file to your completed design as a simulation file.
Simulate the design in Vivado as any simulation type (behavior, postsynthesis/implementation). Set the simulation time to run 2,000,000 ns under Simulation
Settings.
Maximize your simulation waveform window.
Zoom out until you see the CLK waveform (clock should be cycling), at about 10ns
minor tick marks or 50ns labels.
Visit an interesting time-slice, take a screen shot, and describe for your report. This
should be a point where one of the other output signals changed, and note why it
changed, see simex.png.
The point of this step is to just become familiar with the simulator in Vivado.
Report:
Make sure to format your report and answer all of the sections as last time.
1. Zoom in on the alarm_fsm modules in your RTL Schematic by double clicking on the
+. Describe and relate to your Verilog code.
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2. Include 4 screen shots, 1 each for RTL Schematic, Zoomed RTL Schematic
(alarm_fsm), Design, and Simulation. Briefly (2 sentences max) explain each.
3. Relate the Design screenshot to the Design screenshot from Lab1, does this lab
utilize more or less of the board when compared to Lab 1?
4. What is the significance of the number in the line of code below (from lab2.v: module
seconds_clkdiv)? What is the purpose of this line of code? What will happen if this
value is changed?
If (counter == 32’h5F5E110)
5. Briefly (2-3 sentences max) describe how the modules work together. What is the
purpose of button_debouncer?
6. In Lab 1 we saw that each of the functions of the calculator were being performed
in parallel and only one of the functions was displayed for output, as selected by
the button. In this lab are there any significant calculations being performed in
parallel?
Bonus!
+5 Points – Implement Snooze
Add logic so that when, and only when, an alarm is going off, pressing BTN[4] turns off
the alarm and adds 5 minutes (or your favorite snooze time) to the next alarm time to
go off. Make sure that it doesn’t increment the actual, saved alarm time, but rather sets
(or increments) a snoozing flag. You will have to change the structural design of the code
for the alarm_fsm and add additional logic and wires. Make sure to add BTN[4] to your
alarm_clock module.
+5 Points – Dual Displays
The alarm clock has two alarms, but the user doesn’t know which one is set to go off
next. Utilize the left 4 seven-segment displays to show the next time that an alarm will
go off. Make sure that the alarms are enabled via the switches, and after an alarm goes
off or the alarm time is modified, the time displayed on the left display changes. You will
need to modify the sevenSegDisplay module, which sets the left displays via the
segmentFormatter for anodes 4-7 to your next alarm value. The sevenSegDisplay module
will also need to be changed to receive the next alarm value. If no alarm is set, make sure
to display blanks. One hint is to create a new set of wires for the next alarm and a new
module that takes both alarm wires, switches, and current time, and sets the next alarm
wires.