Simulation of Digital Clock Program in 8085

Digital Clock Program -12/24 Hours

Aim : To write an assembly language program to simulate digital clock using 8085.

Theory: The hours, minutes, and seconds are entered at the memory locations which is in decimal form. The enetered data is converted into the format from decimal. A delay of exactly one second is generated and after each delay, the seconds, minutes and hours information is updated. The processing of data is done in hex. form and converted back into decimal before displaying.

Algorithm : Step 1: Start the program. Step 2: Load seconds, minutes and hours in the memory. Step 3: Display hours, minutes and seconds. Step 4: Convert time information into Hex. format from decimal. Step 5: Call delay routine for exactly one second. Step 6: Increment seconds. Step 7: If second is greater than 60, reset seconds to ’00’ and increment minutes. Step 8: If minutes is greater than 60, reset minutes to ’00’ and increment hours. Step9: If hour is greater than24, reset second, minutes, hours to ’00’. Step 10: Convert time information back into decimal format. Step 11: Go to step 3. Step 12. Stop the program.

Befin Skaria

Program Mem. Addrs:

OpCode

8800 8801 8802 8803

21 00 00 22

8804 8805 8806

EF 8F CD

8807 8808 8809 880A 880B 880C 880D 880E 880F

00 80 0E 00 79 32 F1 8F CD

8810 8811 8812

Label Mnemonics

Comments

LXI H,0000

[HL] [0000]

SHLD 8FEF

The contents of register of L are stored athe mem. Location specified and the contents of register H are stored at the next mem. Location by inc. the operand by 1

CALL 8000

Call 8000 contnet (Update the data in address field)

MVI C, 00

[C] 00

MOV A,C STA 8FF1

[A] [C] [8FF1] [A]

CALL 8010

Call 8010 content (Updating to the data field)

10 80 CD

CALL 8020

Call 8020 content (Creating a delay exactly for one sec.)

8813 8814 8815 8816

20 80 79 3C

MOV A,C INR A

8817 8818 8819 881A 881B 881C 881D 881E 881F

27 4F FE 60 C2 0B 88 7D 3C

DAA MOV C,A CPI 60

[A] [C] [A] [A]+01 (Increment content of the acc. By one) Decimal adjust acc. [C] [A] Compare immediate with every 60

JNZ 880B

If [Z]≠0, go to 880B

MOV A,L INR A

8820 8821 8822

27 6F FE

DAA MOV L,A CPI 60

[A] [L] [A] [A]+01 (Increment content of the acc. By one) Decimal adjust acc. [L] [A] Compare immediate with every 60

L1:

L2:

Befin Skaria

8823 8824 8825 8826 8827

60 C2 0B 88 AF

JNZ 880B

If [Z]≠0, go to 880B

XRA A

8828 8829 882A

4F 7E 3C

MOV C,A MOV A,M INR A

The contents of the register exclusive or with the acc. [C] [A] [A] [M] [A] [A]+01 (Increment content of the acc. By one)

882B 882C 882D 882E 882F 8830 8831 8832 8833 8834

27 77 EC 24 C2 0B 88 C3 03 88

DAA MOV M,A CPI 24

[M] [A] Compare immediate with every 24

JNZ 880B

If [Z]≠0, go to 880B

JMP 8803

If [Z]≠0, go to 8803

CALL UPDAD 8000 8001 8002 8003 8004 8005 8006 8007 8008 8009 800A 880B

E5 D5 C5 F5 CD 40 04 F1 C1 D1 E1 C9

PUSH H PUSH D PUSH B PUSH PSW CALL 0440

E5 D5 C5 F5 CD 4C 04 F1 C1 D1 E1 C9

PUSH H PUSH D PUSH B PUSH PSW CALL 044C

11 FF

LXI D, FFFF

POP PSW POP B POP D POP H RET

CALL UPDDT 8010 8011 8012 8013 8014 8015 8016 8017 8018 8019 801A 801B

POP PSW POP B POP D POP H RET

CALL DELAY 8020 8021

Befin Skaria

8022 8023 8024 8025 8026 8027 8028 8029 802A 802B 802C 802D 802E 802F 8030

FF 1B 7A AB C2 23 80 11 00 90 1B 7A AB C2 C9

DCX D MOV A,D XRA E JNZ 8023

LXI D, 9000

DCX D MOV A,D XRA E JNZ 802C RET

Befin Skaria