Date Display Subsystem

8/10/2019 Date Display Subsystem

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Date Display Subsystem

Mohd Zulhilmi Bin Ramli

Universiti Teknologi MalaysiaFaculty of Electrical Engineering

Abstract - In a standard calendar system, the number of

days in a month is either 28, 29, 30 or 31. For example, the

number of days for February is 28 for common year and

29 for leap year. In this project, a system which can

determine the number of days in a month and whether a

given year is a leap year is designed. Leap years are all the

years divisible by 4, except that years divisible by 100 are

not leap years. Years divisible by 400 are also leap years.

As an example, the year 1900 is not a leap year because it

is divisible by 100 but not divisible by 400.

1. INTRODUCTION

Leap Years are needed to keep our calendar in alignment

with the Earth's revolutions around the sun. It takes the Earth

approximately 365.242199 days or 365 days, 5 hours, 48

minutes, and 46 seconds (a tropical year) to circle once

around the Sun. However, the Gregorian calendar has only

365 days in a year, so if we didn't add a day on February 29

nearly every 4 years, we would lose almost six hours off our

calendar every year. After only 100 years, our calendar would

be off by approximately 24 days [1].

In this project, a calendar system is designed so that it

should be able to display the number of days using two 7-

segment displays and a red LED to show whether the given

year is leap year or not. The month number is set by four

toggle switches according to binary number system. The 4-

digit year is represented in BCD number format, and is set

using 14 toggle switches. The 14 toggle switches is called as

YM2YM1 (millennium digit - assume YM8 and YM4 are

tight to logic 0), YH8YH4YH2YH1 (hundredth digit),

YT8YT4YT2YT1 (tenth digit), YO8YO4YO2YO1 (ones

digit). After the month and year values have been set, the

system will display the number of days on two 7-segment

displays and a red LED if the year is a leap year.

In example if the 14 toggle switches is set to

01100110010010 which is represent 1992 in decimal, the red

LED will light on indicating the year is a leap year. If the

remaining 4 toggle switches is set to respective month in

binary, it will shows the number of days in the particular

month. If it was set to 0010 which is February, the 7-segment

displays will show 29. This imply that February is the leap

month. However in this project the leap month is swapped

with March. That mean when 0011 is entered, it will shows 29

if the year is leap year.

2. MATERIALS AND METHOD

The very first step in designing this system is identify the

input and output of the system.

Figure 1: Input Output Diagram of the System

The figure above show the IOBD of the system. From the

diagram there are 14 inputs of the system, 10 inputs for the

Year and 4 inputs for the Month. Since this is combinationa

circuit, no clock is needed.

Next, a truth table based on the condition for the leap to

occur is constructed. According to the condition, a leap year is

occurred if the year is divisible by 4. However, if the year is

divisible by 100 and not divisible by 400, that particular year

is not a leap year. Therefore, there is 3 set of rules need to be

designed for the condition to meet.

The first set of rule is need to detect numbers 0, 4, 8 for

LSB digit, and numbers 2, 6. Need to detect whether tens digit

(the next LSB digit) is even or odd.

LED

Days

Year

Month

Date

Display

Subsystem


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Next, the truth table for the month entered producing

output of the number of the days is designed. For each month

entered, the 7-segment display will shows the number of day

at that particular month. In example, if the input for month is

entered as 0001, the output will be 31, indicating January has

31 days.

From the first rule, the obtained logic gates is as follow:

Y08 Y04 Y02 Y01 F1

0 0 0 0 1

0 0 0 1 0

0 0 1 0 0

0 0 1 1 0

0 1 0 0 1

0 1 0 1 0

0 1 1 0 0

0 1 1 1 0

1 0 0 0 1

1 0 0 1 0

1 0 1 0 0

1 0 1 1 0

1 1 0 0 01 1 0 1 0

1 1 1 0 0

1 1 1 1 0

Table 1: 0, 4, 8

Y08 Y04 Y02 Y01 F2

0 0 0 0 1

0 0 0 1 0

0 0 1 0 1

0 0 1 1 0

0 1 0 0 1

0 1 0 1 0

0 1 1 0 10 1 1 1 0

1 0 0 0 1

1 0 0 1 0

1 0 1 0 0

1 0 1 1 0

1 1 0 0 0

1 1 0 1 0

1 1 1 0 0

1 1 1 1 0

Table 2: Even 2nd

LSB

Y08 Y04 Y02 Y01 F3

0 0 0 0 00 0 0 1 0

0 0 1 0 1

0 0 1 1 0

0 1 0 0 0

0 1 0 1 0

0 1 1 0 1

0 1 1 1 0

1 0 0 0 0

1 0 0 1 0

1 0 1 0 0

1 0 1 1 0

1 1 0 0 0

1 1 0 1 0

1 1 1 0 0

1 1 1 1 0

Table 3: 2, 6

Y08 Y04 Y02 Y01 F4

0 0 0 0 00 0 0 1 1

0 0 1 0 0

0 0 1 1 1

0 1 0 0 0

0 1 0 1 1

0 1 1 0 0

0 1 1 1 1

1 0 0 0 0

1 0 0 1 1

1 0 1 0 0

1 0 1 1 0

1 1 0 0 0

1 1 0 1 01 1 1 0 0

1 1 1 1 0

Table 4: Odd 2nd

LSB

Figure 2: Logic equivalent of first rule

The second rule is obtained as follow:

Y08 Y04 Y02 Y01 F5

0 0 0 0 1

0 0 0 1 0

0 0 1 0 0

0 0 1 1 0

0 1 0 0 0

0 1 0 1 0

0 1 1 0 0

0 1 1 1 0

1 0 0 0 0

1 0 0 1 0

1 0 1 0 0

1 0 1 1 0


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1 1 0 0 0

1 1 0 1 0

1 1 1 0 0

1 1 1 1 0

Table 5: Divisible by 100

Figure 3: Logic equivalent of second rule

The third rule is obtained by using similar step as

Divisible by 4, but this time the output is AND with Divisible

by 100.

Figure 4: Logic equivalent of the third rule

According to the condition, a leap year is occurred if the

year is divisible by 4. However, if the year is divisible by 100

and not divisible by 400, that particular year is not a leap year.

Combining all these rules resulting the following output:

Figure 5: The leap logic

If the year is leap year, the Leap output will become 1,

turning the LED on. Else, the output is 0.

Next, the Leap output is combined with the input of the

Month. The truth table is constructed. For this project, we

swapped February with March.

A3 A2 A1 A0 D4 D3 D2 D1 D0

0 0 0 0 0 0 0 0 0

0 0 0 1 1 1 1 1 1

0 0 1 0 1 1 1 1 1

0 0 1 1 1 1 1 0 0 (1)

0 1 0 0 1 1 1 1 0

0 1 0 1 1 1 1 1 1

0 1 1 0 1 1 1 1 0

0 1 1 1 1 1 1 1 1

1 0 0 0 1 1 1 1 1

1 0 0 1 1 1 1 1 01 0 1 0 1 1 1 1 1

1 0 1 1 1 1 1 1 0

1 1 0 0 1 1 1 1 1

1 1 0 1 0 0 0 0 0

1 1 1 0 0 0 0 0 0

1 1 1 1 0 0 0 0 0

Table 6: Month and its respective number of days

The output with the bracket indicates that month is leap

month. The equivalent logic gates is as follow.

Figure 6: Input for month


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The output D4 to D0 is represented in BCD. Before this

output is connected to 7-segment display, it first split into

single digit.

Leap D2 D1 D0 O3 O2 O1 O0

0 0 0 0 0 0 0 0

0 0 0 1 0 0 0 0

0 0 1 0 0 0 0 0

0 0 1 1 0 0 0 0

0 1 0 0 1 0 0 0

0 1 0 1 1 0 0 1

0 1 1 0 0 0 0 0

0 1 1 1 0 0 0 1

1 0 0 0 0 0 0 0

1 0 0 1 0 0 0 0

1 0 1 0 0 0 0 0

1 0 1 1 0 0 0 0

1 1 0 0 0 0 0 0

1 1 0 1 0 0 0 0

1 1 1 0 0 0 0 0

1 1 1 1 0 0 0 0

Table 7: Splitting Month output to BCD for LSB

From the table, the desired output is only 28, 29, 30 and

31. However, for 29, it is interchanged during leap year,

separated by multiplexer.

Figure 7: BCD output

Figure above is the final output of the system. It is

attached to 7446 BCD to 7-segment display so the display can

show the correct numbers. The mux input is only attached to

IN0 and IN1 because the rest of the input is not needed.

After the system is successfully implemented, the system

is compiled in Quartus II.

Figure 8: Compilation result

After the compilation, the system is assigned with the pin

provided by the board. In this project, Altera DE2 FPGA

which is using Cyclone II chip is used [2].

Figure 9: Pin Assignment

After completed the pin assignment, the project is

recompiled. When compilation is completed, the project is


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uploaded into the board using build in programmer. Final step

is the system is tested on the board.

3. RESULT

The board is tested by set the year and the month. Both

leap and non-leap year is tested.

Figure 10: Leap year and February days

Figure 11: Leap year and March days

Figure 12: leap year and June days

From the figure above, the year is set to leap year and the

LED is light on indicates the year is leap. Figure 10 shows

February, showing 31 days. Figure 11 is March, has 29 days

because it is leap month and finally figure 12 is June, has 30

days.

Figure 13: Non-leap year and June days


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Figure 14: Non-leap year and March days

Figure 15: Non-leap year and January days

From the figure above, the year is set to non-leap year and

the LED is light off indicates the year is non-leap. Figure 13

shows June, showing 30 days. Figure 14 is March, has 28 days

because it is non-leap month and finally figure 15 is January,

has 31 days.

4. DISCUSSION

Figure 10, 11, and 12 show a leap year indicator on

because it met the condition the system imposed which is

All year divisible by 4 is leap year, except for the year

that divisible by 100 but not divisible by 400.

The year in those figure is 2000. Comparing it to the

conditions, 2000 is divisible by 4. It also divisible by both 100

and 400. Therefore the year is a leap year.

For figure 13, 14 and 15, the leap year indicator is off

because the year set is not a leap year, which is 2001. This is

due to 2001 is not divisible by 4.

For the number of day, referring to Table 6 and Figure 6

the input is valid only from 1 to 12. Any than that will yield 0.

From figure 10, the input for month is 0010. Looking back at

the truth table in Table 6, it will give output of 11111, which is

31 in decimal. The rest of the month will give it respective

days, as in Table 6. Exception is during leap year, where the

output for last bit of number of day is interchanged if the year

is leap year. For example, during non-leap year, March last bi

is 0. However during leap year, the 0 is interchanged with 1

using multiplexer.

5.

CONCLUSION

From the result, it can be concluded that the system

designed successfully emulate the Date Display Subsystem

with Leap Year Indicator. For any year is inserted, the system

will automatically detect whether the system is leap year or

not and for any month inserted, it also display the number o

month in that particular month.

6.

REFERENCE

[1] http://www.timeanddate.com/date/leapyear.html

[2] Dr. Rabia Bakhteri, VLSI System Design Lab,

Faculty of Electrical Engineering, Universiti

Teknologi Malaysia, 2014
http://www.timeanddate.com/date/leapyear.htmlhttp://www.timeanddate.com/date/leapyear.htmlhttp://www.timeanddate.com/date/leapyear.html

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Date Display Subsystem