Experiment 1 BT-40 Deboleena Roy 09EC3203 Shruti Khatri 09EC1057
Experiment 1: Familiarization with 8051 kit Objective: Study about the kit components and its interface with the PC. Write the following programs in the assembly language of 8051. 1. Find the second largest of an array of 100 numbers stored in external memory from location 9000H onwards. The number be stored at location 9500H. Show the contents of memory locations before and after running the pro gram to establish correctness of it 2. Compute the LCM of two numbers. Assume the numbers to be stored at location 9000H and 9001H. Store the result at 9002H. 3. Check whether a NULL-terminated string stored from location 9000H is a palindrome or not. If the string is a palindrome, store 1 at location 9500H, else clear the location.
Apparatus and Software Software 1. ESA51E 8051 Trainer Board 2. Compiler – Compiler – Kiel Kiel µVision4 3. Driver – Driver – Win51E Win51E
Design (Hardware) ESA51E is trainer kit that is interfaced with PC through RS-232-C serial port connection. It is provided external power supply of +5V. The compiler converts the assembly code into a .hex file which is then loaded on the code space of 8051 using driver Win51E
Design (Software) Part 1: Obtain second largest number numbe r from an array of 100 numbers Design 1. 2. 3. 4. 5. 6. 7. 8.
For the first number, read it and store it in R1. Now, input the next number in R3. Copy content of R1 at some random location, say 60H. If R3 = value at 60H, R2= R3. If R3 > value at 60H, R1 = R3; R2 = value at 60h. If R3 < value at 60H, and R3 > R2; R2 = R3. Loop End
Experiment 1 BT-40 Deboleena Roy 09EC3203 Shruti Khatri 09EC1057
Software Code ORG 8100H MOV DPTR,#9000H MOV R0,#99 MOVX A,@DPTR MOV R1,A INC DPTR MOVX A,@DPTR MOV 60H,R1 CJNE A,60H,NEXT MOV R2,A SJMP LOOP NEXT: JNC SHIFT MOV R2,A SJMP LOOP SHIFT: MOV R3,A MOV A,R1 MOV R2,A MOV A,R3 MOV R1,A LOOP: DJNZ R0,MAIN SJMP FINISH MAIN: INC DPTR MOVX A,@DPTR MOV 60H,R1 CJNE A,60H,NEXT2 MOV R2,A SJMP LOOP NEXT2: JNC SHIFT MOV 60H,R2 CJNE A,60H,NEXT3 SJMP LOOP NEXT3: JNC MOVR2A SJMP LOOP MOVR2A:
MOV R2,A SJMP LOOP
Experiment 1 BT-40 Deboleena Roy 09EC3203 Shruti Khatri 09EC1057
FINISH: MOV DPTR,#9500H MOV A,R2 MOVX @DPTR,A HERE: SJMP HERE END
Part 2: Find the LCM of 2 given numbers Design 1.
5.
Input the numbers in R1 and R2. If R1 < R2, interchange the values. Store A = R1, B = R2. Perform the following until B = 0 is satisfied. a. Store B at some location say 60h b. Divide A by B. c. Store B’s value in A, and store the remainder in B. d. Loop GCD = value at 60H.
6.
Obtain LCM by using the formula,
7.
END
2. 3. 4.
Software Code ORG 8100H MOV DPTR,#9000H MOVX A,@DPTR MOV R1,A INC DPTR MOVX A,@DPTR MOV R2,A MOV 60H,R1 CJNE A,60H, NEXT1 SJMP LEAVE NEXT1: JNC SWITCH MOV A,R1 MOV B,R2 SJMP LOOP SWITCH:
MOV A,R1
.
Experiment 1 BT-40 Deboleena Roy 09EC3203 Shruti Khatri 09EC1057
MOV R3,A MOV A,R2 MOV R1,A MOV A,R3 MOV R2,A MOV A,R1 MOV B,R2 LOOP:
MOV R4,B DIV AB MOV A,B JZ GCDOUT MOV A,R4 SJMP LOOP
GCDOUT:
MOV A,R1 MOV B,R4 DIV AB MOV B,R2 MUL AB
LEAVE:
INC DPTR MOVX @DPTR,A INC DPTR MOV A,B MOVX @DPTR,A
HERE: SJMP HERE END Part 3: Find out whether a given string is a palindrome Design 1. Obtain the string length by reading till NULL is obtained, and running a counter alongside. 2. Start reading character by character. 3. Store 1st character at location 70H and corresponding mirror image in A. Compare and if same, continue to next character. If not, exit loop. Go to step 5 4. If the entire string is scanned (R1=0), then exit loop. Move #1 to 9500H. 5. END
Experiment 1 BT-40 Deboleena Roy 09EC3203 Shruti Khatri 09EC1057
Software Code ORG 8100H MOV R2,#0H MOV DPTR,#8FFFH ;1 less than starting value STRING: INC R2 INC DPTR MOVX A,@DPTR CJNE A,#0H,STRING DEC DPL MOV R0,DPL MOV A,R2 MOV B,#2H DIV AB MOV R2,A MOV DPTR,#9000H LOOP: MOVX A,@DPTR MOV R4,DPL MOV 70H,A MOV DPL,R0 MOVX A,@DPTR CJNE A,70H,LEAVE DEC DPL MOV R0,DPL MOV DPL,R4 INC DPTR DJNZ R2,LOOP MOV DPTR,#9500H MOV A,#01H MOVX @DPTR,A LJMP NEXT LEAVE: MOV DPTR,#9500H MOV A,#0H MOVX @DPTR,A NEXT: SJMP NEXT END
Experiment 1 BT-40 Deboleena Roy 09EC3203 Shruti Khatri 09EC1057
Observation To work with user given data, and to verify the functionality of the code, we can use the software package to view and edit the registers of the microcontroller. Next, by running the program over the inserted values we can validate the code. Part 1: User Input Address 9000H 9001H 9002H 9003H 9004H … … … 9063H
Value 00H 50H 60H 70H 00H . . . 00H
Output Address 9500H
Value 60H
Part 2: User Input Address 9000H 9001H
Value 06H (6) 0AH (10)
Output Address 9002H
Value 1EH (30)
Experiment 1 BT-40 Deboleena Roy 09EC3203 Shruti Khatri 09EC1057
Part 3: Case 1 User Input Address 9000H 9001H 9002H 9003H 9004H 9005H
Value 03H 02H 01H 02H 03H 00H
Output Address 9500H
Value 01H (it is a palindrome)
Case 2 User Input Address 9000H 9001H 9002H 9003H 9004H 9005H
Value 03H 02H 00H 02H 03H 00H
Output Address 9500H
Value 00H (it is not palindrome)
The program reads the string up to 9001H as it encounters the null character at 9002H. So it sees the string as ‘03’ ‘02’ which is not a palindrome
Experiment 1 BT-40 Deboleena Roy 09EC3203 Shruti Khatri 09EC1057
Discussion Deboleena Roy 09EC3203 1. The program is written in assembly language. Usual conditional constructs like if … else, for, do … while are replaced by intuitive register transfers and jumps. 2. Mathematical operations, transfer of values with external RA M (MOVX), comparisons are restricted to Register Accumulator (A) 3. Each program is executed by first setting the program counter to start of the location of the code in code space. In our case it is 8100 H 4. Each program terminates with an infinite loop of the type NEXT: JUMP NEXT so that the PC remains stuck there and no further instructions in other parts of the code space gets executed. 5. CJNE function was abundantly used in all 3 parts. The syntax is CJNE value#1, value#2. Value#1 must always be A (accumulator). Carry bit is set to 1 if A < value#2 else it is set to zero.
Shruti Khatri 09EC1057 1. In this experiment, we wrote and burned basic programs on the 8051 micro-controller. 2. Syntax used in assembly language is not very intuitive. Most operations don't work on registers and the accumulator has to be used during the operation and the result needs to be copied in the register. Same is the case with operations like compare which doesn't work on registers. 3. When writing the program we should always make sure that the program ends with an infinite loop otherwise on running the code some instructions that are already present at memory locations that we haven't re-written might be executed. We should press break to stop the execution of the infinite loop and see the results. 4. When performing compare operation the value of carry varies depending on whether greater than or less than is true and this can be used in the program. 5. The program counter should be set in the WIN51E environment at the location from which we want the program to execute.
