2. Numerical Bases Used in Programming Hexadecimal Binary BCD

3. Hexadecimal Basis Hexadecimal Digits: 1 2 3 4 5 6 7 8 9 A B C D E F A=10 B=11 C=12 D=13 E=14 F=15

4. Decimal, Binary, BCD, & Hexadecimal Numbers (43) 10 = (0100 0011) BCD = ( 0010 1011 ) 2 = ( 2 B ) 16

5. Registers A B R0 R1 R3 R4 R2 R5 R7 R6 DPHDPL PC DPTR PC Some 8051 16-bit Register Some 8-bitt Registers of the 8051 SP

6. Memory mapping in 8051 ROM memory map in 8051 family 0000H 0FFFH 0000H 1FFFH 8751 AT89C51 8752 AT89C52 4k8k

7. RAM memory space allocation in the 8051 7FH 30H 2FH 20H 1FH 17H 10H 0FH 07H 08H 18H 00H Register Bank 0 (Stack) Register Bank 1 Register Bank 2 Register Bank 3 Bit-Addressable RAM Scratch pad RAM

8. Addressing Modes Register Direct Register Indirect Immediate Relative Absolute Long Indexed

9. Register Addressing Mode MOVRn, A;n=0,..,7 ADDA, Rn MOVDPL, R6 MOVDPTR, A MOVRm, Rn

10. Direct Addressing Mode Although the entire of 128 bytes of RAM can be accessed using direct addressing mode, it is most often used to access RAM loc. 30 – 7FH. MOVR0, 40H MOV56H, A MOVA, 4; ≡ MOV A, R4 MOV6, 2; copy R2 to R6 ; MOV R6,R2 is invalid !

11. Register Indirect Addressing Mode In this mode, register is used as a pointer to the data. MOVA,@Ri; move content of RAM loc. where address is held by Ri into A ( i=0 or 1 ) MOV@R1,B In other word, the content of register R0 or R1 is sources or target in MOV, ADD and SUBB insructions.

12. Immediate Addressing Mode MOVA,#65H MOVR6,#65H MOVDPTR,#2343H MOVP1,#65H

13. Relative, Absolute, & Long Addressing Used only with jump and call instructions: SJMP ACALL,AJMP LCALL,LJMP

14. Indexed Addressing Mode This mode is widely used in accessing data elements of look-up table entries located in the program (code) space ROM at the 8051 MOVCA,@A+DPTR (A,@A+PC) A= content of address A +DPTR from ROM Note: Because the data elements are stored in the program (code ) space ROM of the 8051, it uses the instruction MOVC instead of MOV. The “C” means code.

15. Some Simple Instructions MOV dest,source ; dest = source MOV A,#72H;A=72H MOV R4,#62H;R4=62H MOV B,0F9H;B=the content of F9’th byte of RAM MOV DPTR,#7634H MOV DPL,#34H MOV DPH,#76H MOV P1,A;mov A to port 1 Note 1: MOV A,#72H ≠ MOV A,72H After instruction “MOV A,72H ” the content of 72’th byte of RAM will replace in Accumulator. Note 2: MOV A,R3≡MOV A,3

16. ADDA, Source;A=A+SOURCE ADDA,#6;A=A+6 ADDA,R6;A=A+R6 ADD A,6;A=A+[6] or A=A+R6 ADDA,0F3H;A=A+[0F3H] SUBBA, Source;A=A-SOURCE-C SUBB A,#6;A=A-6 SUBB A,R6;A=A+R6

17. MUL & DIV MULAB ;B|A = A*B MOVA,#25H MOVB,#65H MULAB;25H*65H=0E99 ;B=0EH, A=99H DIVAB;A = A/B, B = A mod B MOVA,#25 MOVB,#10 DIVAB;A=2, B=5

18. SETBbit; bit=1 CLRbit; bit=0 SETBC; CY=1 SETBP0.0;bit 0 from port 0 =1 SETBP3.7;bit 7 from port 3 =1 SETBACC.2;bit 2 from ACCUMULATOR =1 SETB05;set high D5 of RAM loc. 20h Note: CLR instruction is as same as SETB i.e.: CLRC;CY=0 But following instruction is only for CLR: CLRA;A=0

19. DECbyte;byte=byte-1 INCbyte;byte=byte+1 INCR7 DECA DEC40H; [40]=[40]-1

20. RR – RL – RRC – RLC A EXAMPLE: RRA RR: RRC: RL: RLC: C C

21. ANL - ORL – XRL Bitwise Logical Operations: AND, OR, XOR EXAMPLE: MOVR5,#89H ANLR5,#08H CPLA;1’s complement Example: MOVA,#55H;A=01010101 B L01:CPLA MOVP1,A ACALLDELAY SJMPL01

22. Stack in the 8051 The register used to access the stack is called SP (stack pointer) register. The stack pointer in the 8051 is only 8 bits wide, which means that it can take value 00 to FFH. When 8051 powered up, the SP register contains value 07. 7FH 30H 2FH 20H 1FH 17H 10H 0FH 07H 08H 18H 00H Register Bank 0 (Stack) Register Bank 1 Register Bank 2 Register Bank 3 Bit-Addressable RAM Scratch pad RAM

23. Example: MOVR6,#25H MOVR1,#12H MOVR4,#0F3H PUSH6 PUSH1 PUSH4 0BH 0AH 09H 08H Start SP=07H 25 0BH 0AH 09H 08H SP=08H F3 12 25 0BH 0AH 09H 08H SP=08H 12 25 0BH 0AH 09H 08H SP=09H

24. LOOP and JUMP Instructions JZJump if A=0 JNZJump if A/=0 DJNZDecrement and jump if A/=0 CJNE A,byteJump if A/=byte CJNE reg,#dataJump if byte/=#data JCJump if CY=1 JNCJump if CY=0 JBJump if bit=1 JNBJump if bit=0 JBCJump if bit=1 and clear bit Conditional Jumps :

25. DJNZ: Write a program to clear ACC, then add 3 to the accumulator ten time Solution: MOVA,#0 MOVR2,#10 AGAIN:ADDA,#03 DJNZR2,AGAIN ;repeat until R2=0 (10 times) MOVR5,A

26. LJMP(long jump) LJMP is an unconditional jump. It is a 3-byte instruction. It allows a jump to any memory location from 0000 to FFFFH. AJMP(absolute jump) In this 2-byte instruction, It allows a jump to any memory location within the 2k block of program memory. SJMP(short jump) In this 2-byte instruction. The relative address range of 00- FFH is divided into forward and backward jumps, that is, within -128 to +127 bytes of memory relative to the address of the current PC.

27. CALL Instructions Another control transfer instruction is the CALL instruction, which is used to call a subroutine. LCALL(long call) This 3-byte instruction can be used to call subroutines located anywhere within the 64K byte address space of the 8051. ACALL (absolute call) ACALL is 2-byte instruction. the target address of the subroutine must be within 2K byte range.

28. Example: Write a program to copy a block of 10 bytes from RAM location starting at 37h to RAM location starting at 59h. Solution: MOV R0,#37h; source pointer MOV R1,#59h; dest pointer MOV R2,#10; counter L1: MOV A,@R0 MOV @R1,A INC R0 INC R1 DJNZ R2,L1

29. .100's10's1's.156 +248 =404 Decimal Addition 156 + 248 16 Bit Addition 1A44 + 22DB.256's16’s 1's.1 A4 +2 D B =3 D1 F = 3D1F

30. Performing the Addition with 8051.65536's256's1's.R6R7 +R4R5 =R1R2R3 1.Add the low bytes R7 and R5, leave the answer in R3. 2.Add the high bytes R6 and R4, adding any carry from step 1, and leave the answer in R2. 3.Put any carry from step 2 in the final byte, R1.

31. Steps 1, 2, 3 MOV A,R7 ;Move the low-byte into the accumulator ADD A,R5 ;Add the second low-byte to the accumulator MOV R3,A ;Move the answer to the low-byte of the result MOV A,R6 ;Move the high-byte into the accumulator ADDC A,R4 ;Add the second high-byte to the accumulator, plus carry. MOV R2,A ;Move the answer to the high-byte of the result MOV A,#00h ;By default, the highest byte will be zero. ADDC A,#00h ;Add zero, plus carry from step 2. MOV R1,A ;Move the answer to the highest byte of the result

32. The Whole Program ;Load the first value into R6 and R7 MOV R6,#1Ah MOV R7,#44h ;Load the first value into R4 and R5 MOV R4,#22h MOV R5,#0DBh ;Call the 16-bit addition routine LCALL ADD16_16 ADD16_16: ;Step 1 of the process MOV A,R7 ;Move the low-byte into the accumulator ADD A,R5 ;Add the second low-byte to the accumulator MOV R3,A ;Move the answer to the low-byte of the result ;Step 2 of the process MOV A,R6 ;Move the high-byte into the accumulator ADDC A,R4 ;Add the second high-byte to the accumulator, plus carry. MOV R2,A ;Move the answer to the high-byte of the result ;Step 3 of the process MOV A,#00h ;By default, the highest byte will be zero. ADDC A,#00h ;Add zero, plus carry from step 2. MOV MOV R1,A ;Move the answer to the highest byte of the result ;Return - answer now resides in R1, R2, and R3. RET

33. Timer & Port Operations Example: Write a program using Timer0 to create a 10khz square wave on P1.0 MOV TMOD,#02H;8-bit auto-reload mode MOV TH0,#-50;-50 reload value in TH0 SETB TR0;start timer0 LOOP:JNB TF0, LOOP;wait for overflow CLR TF0;clear timer0 overflow flag CPL P1.0;toggle port bit SJMP LOOP;repeat END

34. Interrupts 1.Enabling and Disabling Interrupts 2.Interrupt Priority 3.Writing the ISR (Interrupt Service Routine)

35. Interrupt Enable (IE) Register : EA : Global enable/disable. --- : Undefined. ET2 :Enable Timer 2 interrupt. ES :Enable Serial port interrupt. ET1 :Enable Timer 1 interrupt. EX1 :Enable External 1 interrupt. ET0 : Enable Timer 0 interrupt. EX0 : Enable External 0 interrupt.

36. Interrupt Vectors InterruptVector Address System Reset0000H External 00003H Timer 0000BH External 10013H Timer 1001BH Serial Port0023H Timer 2002BH

37. Writing the ISR Example: Writing the ISR for Timer0 interrupt ORG 0000H;reset LJMP MAIN ORG 000BH;Timer0 entry point T0ISR:.;Timer0 ISR begins. RETI;return to main program MAIN:.;main program. END

38. Structure of Assembly language and Running an 8051 program EDITOR PROGRAM ASSEMBLER PROGRAM LINKER PROGRAM OH PROGRAM Myfile.asm Myfile.obj Other obj file Myfile.lst Myfile.hex

39. Examples of Our Program Instructions MOV C,P1.4 JC LINE1 SETB P1.0 CLR P1.2

40. 8051 Instruction Set ACALL: Absolute Call ADD, ADDC: Add Acc. (With Carry) AJMP: Absolute Jump ANL: Bitwise AND CJNE: Compare & Jump if Not Equal CLR: Clear Register CPL: Complement Register DA: Decimal Adjust DEC: Decrement Register DIV: Divide Accumulator by B DJNZ: Dec. Reg. & Jump if Not Zero INC: Increment Register JB: Jump if Bit Set JBC: Jump if Bit Set and Clear Bit JC: Jump if Carry Set JMP: Jump to Address JNB: Jump if Bit Not Set JNC: Jump if Carry Not Set JNZ: Jump if Acc. Not Zero JZ: Jump if Accumulator Zero LCALL: Long Call LJMP: Long Jump MOV: Move Memory MOVC: Move Code Memory MOVX: Move Extended Memory MUL: Multiply Accumulator by B NOP: No Operation ORL: Bitwise OR POP: Pop Value From Stack PUSH: Push Value Onto Stack RET: Return From Subroutine RETI: Return From Interrupt RL: Rotate Accumulator Left RLC: Rotate Acc. Left Through Carry RR: Rotate Accumulator Right RRC: Rotate Acc. Right Through Carry SETB: Set Bit SJMP: Short Jump SUBB: Sub. From Acc. With Borrow SWAP: Swap Accumulator Nibbles XCH: Exchange Bytes XCHD: Exchange Digits XRL: Bitwise Exclusive OR Undefined: Undefined Instruction