2. Write an 8051 program to generate a square wave of 25 khz at pin P2.3 using XTAL = 12 MHz. Solution:

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Assignment 2 1. Assume that 5 binary data items are stored in RAM locations starting at 50h, as shown below. Write a program to find the sum of all the numbers.

1 Assignment 2 1. Assume that 5 binary data items are stored in RAM locations starting at 50h, as shown below. Write a program to find the sum of all the numbers. The calculation is in 16-bit format and the result is stored in RAM locations 61h (upper 8-bit) & 60h (lower 8-bit). RAM location 50h = (71) RAM location 51h = (A1) RAM location 52h = (65) RAM location 53h = (59) RAM location 54h = (47) ORG 00H SUM_HB EQU 61H SUM_LB EQU 60H COUNT EQU 5 ; MOV 50H,#71H ; RAM location 50h = (71) MOV 51H,#0A1H ; RAM location 51h = (A1) MOV 52H,#65H ; RAM location 52h = (65) MOV 53H,#59H ; RAM location 53h = (59) MOV 54H,#47H ; RAM location 54h = (47) ; MOV SUM_HB, #0 MOV SUM_LB, #0 MOV R1, #COUNT MOV R0, #50H MOV A, SUM_LB AGAIN ADDC JNC NO_CARRY INC SUM_HB CLR C ; REMEMBER TO CLEAR THE CARRY FLAG NO_CARRY MOV SUM_LB, A ; SAVE IT INC R0 ; POINT TO NEXT LOCATION DJNZ R1, AGAIN NOP 2. Write an 8051 program to generate a square wave of 25 khz at pin P2.3 using XTAL = 12 MHz. Solution The period of the square wave, T = 1/25KHz = 40 us ½ of it for the high and low portions of the pulse = 20 us 20 us / 1µs = 20 timer cycles are needed for each pulse. Timer 1 value to be set = = in decimal = FFECH i.e. TH1 = FFH and TL1 = ECH ( need 16 bit Counter, so take mode 1) Timer 1 is adopted and configured to operate in mode 1 TO GENERATE THIS SQUARE WAVE. MOV TMOD, #10H ; Timer 1, mode 1 AGAIN MOV TL1, #0ECH ; TL1 =ECH -1-

2 MOV TH1, #0FFH ; TH1 =FFH BACK JNB TF1, BACK ; Stay until timer rolls over CLR TR1 ; Stop Timer 1 CPL P2.3 ; Complement P2.3 to set Hi, Low CLR TF1 ; Clear Timer flag by software SJMP AGAIN 3. Re-write the program in Q2 by using timer interrupt method. Solution ORG 0000H LJMP MAIN ;by-pass interrupt vector table ; ISR for Timer 1 to generate square wave ORG 001BH LJMP ISR_T1 ; jump to ISR_T1 ; Main Program for initialization ORG 30H MAIN MOV TMOD, #10H ; Timer 1, mode 1 MOV TL1, #0ECH ; TL1 =ECH MOV TH1, #0FFH ; TH1 =FFH MOV IE, #88H ; enable Timer 1 interrupt HERE SJMP HERE ; Timer 1 ISR ISR_T1 CPL P2.3 ; Complement P2.3 to set Hi, Low MOV TL1, #0ECH ; reload timer value MOV TH1, #0FFH ; I 4. Write an 8051 program to display the 16 hexadecimal characters from 0 to F on a 7-segment display. Assume the 7-segment display is common anode type and is controlled by Port 1. Output port, P Display Dp g f E d c b a segment A b C d E F

ORG 0H START MOV R7,#0 MOV DPTR,#TABLE NEXT MOV A,R7 MOVC A,@A+DPTR MOV P2,A ACALL DELAY INC R7 CJNE R7,#16,NEXT AJMP START DELAY 5. Write a program to control an ADC0804 for data acquisition.

3 ORG 0H START MOV R7,#0 MOV DPTR,#TABLE NEXT MOV A,R7 MOVC MOV P2,A ACALL DELAY INC R7 CJNE R7,#16,NEXT AJMP START DELAY 5. Write a program to control an ADC0804 for data acquisition. The program monitors the ADC0804 INTR pin and brings the digital input value into register A. ORG 0100H TABLE DB B ; 0 DB B ; 1 DB B ; 2 DB B ; 3 DB B ; 4 DB B ; 5 DB B ; 6 DB B ; 7 DB B ; 8 DB B ; 9 DB B ; A DB B ; b DB B ; C DB B ; d DB B ; E DB B ; F ;1=OFF ;0=ON ; P2.6 = WR (Start conversion needs a L-to-H pulse) ; P2.7 = INTR (When low, end-of-conversion) ; P2.5 = RD (H-to-L will read the data from ADC chip) ; P1.0 P1.7 = D0 D7 of the ADC0804 MOV P1, #0FFH ; make P1=input BACK CLR P2.6 ; WR=0 SETB P2.6 ; WR=1 L-to-H to start conversion HERE JB P2.7, HERE ; wait for end of conversion (monitor INTR pin) CLR P2.5 ; conversion finished, enable RD MOV A, P1 ; read the data ACALL DATA_DISPLAY ; display the data (optional) SETB P2.5 ; make RD=1 for next round SJMP BACK 6. With the aid of diagram, brief describe how to use an 8051 microcontroller to regulate the temperature of a room. If the room temperature is above 25 C, the 8051 will give out a signal to switch on the compressor of the air-conditioner. Otherwise, the compressor is OFF. Ventilation fans are on continuously. -3-

4 P2.3 P2.4 Ventilation fans Compressor +5V LM ADC0804 D Q Q D Q Q XTAL1 XTAL2 P2.3 P2.5 P2.4 P2.6 P2.5 P2.6 P2.7 P1.0 P1.7 RD WR INTR D0 D7 V CC CLK R CLK IN V in(+) V in( ) A GND Vref/2 D GND CS Set to 1.6V a. The hardware circuitry for this room application by using microcontroller 8051 is depicted in the above diagram. The ventilation fan and compressor are controlled via solid state relay (SSR) by port P2.3 and P2.4 respectively as shown in this above diagram. Logic 1 is activated to turn on them. From the electrical specification, the temperature range of the temperature sensor LM35 is -55 C to 150 C and its output scale is 10mV/ C. The output value of the ADC0804 is 00H when the LM35 senses -55 C. b. The step size of the ADC0804 = 2 x 1.6 / 255 = mv. c. The minimum output value from the ADC0804 to switch on the compressor of the air-conditioner Dout = [ 25 (-55) ] x 10mV / mV = (take or B ) 8051 assembly programming ORG 00H ; P2.6 = WR (Start conversion needs a L-to-H pulse) ; P2.7 = INTR (When low, end-of-conversion) ; P2.5 = RD (H-to-L will read the data from ADC chip) ; P1.0 P1.7 = D0 D7 of the ADC0804 ; P2.3 = 1, TURN ON VENTILATION FAN, 0=OFF ; P2.4 = 1, TURN ON COMPRESSOR, 0=0FF ; SETB P2.3 ; on the ventilation fan CLR P2.4 ; off the compressor ; MOV P1, #0FFH ; make P1=input BACK CLR P2.6 ; WR=0 SETB P2.6 ; WR=1 L-to-H to start conversion HERE JB P2.7, HERE ; wait for end of conversion CLR P2.5 ; conversion finished, enable RD MOV A, P1 ; read the data -4-

5 ACALL CTL_COMPRESOR SETB P2.5 ; make RD=1 for next round SJMP BACK ; CTL_COMPRESSOR CJNE A,#64, NOT_EQUAL AJMP TURN_ON NOT_EQUAL JNC TURN_ON ; now C=1, ie. A < 64, CLR P2.4 ; off TURN_ON SETB P2.4 ; on start Turn on ventilation fan and off the compressor Configure 8051 input port Read digital reading from ADC device Room Temperature above 25 C? Y N Turn off compressor Turn on compressor -5-

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