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2. Numerical Bases Used in Programming
• Hexadecimal
• Binary
• BCD
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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
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4. Decimal, Binary, BCD, & Hexadecimal Numbers
(43)10=
(0100 0011)BCD=
( 0010 1011 )2 =
(
2
B
)16
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5. Register
s
SP
A
B
R0
DPTR
DPH
DPL
R1
R2
PC
PC
R3
R4
Some 8051 16-bit Register
R5
R6
R7
Some 8-bitt Registers of
the 8051
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6. Memory mapping in 8051
• ROM memory map in 8051 family
4k
0000H
8k
0000H
0FFFH
8751
AT89C51
1FFFH
8752
AT89C52
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7. • RAM memory space allocation in the 8051
7FH
Scratch pad RAM
30H
2FH
Bit-Addressable RAM
20H
1FH
Register Bank 3
18H
17H
Register Bank 2
10H
0FH
08H
Stack) Register Bank 1)
07H
Register Bank 0
00H
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8. Addressing Modes
•
•
•
•
•
•
•
•
Register
Direct
Register Indirect
Immediate
Relative
Absolute
Long
Indexed
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9. Register Addressing Mode
MOV Rn, A
;n=0,..,7
ADD
A, Rn
MOV DPL, R6
MOV DPTR, A
MOV Rm, Rn
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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.
MOV R0, 40H
MOV 56H, A
MOV A, 4
MOV 6, 2
; ≡ MOV A, R4
; copy R2 to R6
; MOV R6,R2 is invalid !
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11. Register Indirect Addressing Mode
• In this mode, register is used as a pointer to the
data.
MOV
A,@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.
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12. Immediate Addressing Mode
MOV A,#65H
MOV R6,#65H
MOV DPTR,#2343H
MOV P1,#65H
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13. Relative, Absolute, & Long Addressing
Used only with jump and call instructions:
SJMP
ACALL,AJMP
LCALL,LJMP
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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
MOVC
A,@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.
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15. Some Simple Instructions
MOV dest,source
; dest = source
MOV A,#72H
MOV R4,#62H
MOV B,0F9H
;A=72H
;R4=62H
;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
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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
ADD
A,0F3H
;A=A+[0F3H]
SUBB
A, Source
;A=A-SOURCE-C
SUBB
A,#6
;A=A-6
SUBB
A,R6
;A=A+R6
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17. MUL & DIV
• MUL
MOV
MOV
MUL
AB ;B|A = A*B
A,#25H
B,#65H
AB
;25H*65H=0E99
;B=0EH, A=99H
• DIV
MOV
MOV
DIV
AB ;A = A/B, B = A mod B
A,#25
B,#10
AB
;A=2, B=5
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18. SETB bit
CLR bit
; bit=1
; bit=0
SETB
SETB
SETB
SETB
SETB
; CY=1
;bit 0 from port 0 =1
;bit 7 from port 3 =1
;bit 2 from ACCUMULATOR =1
;set high D5 of RAM loc. 20h
C
P0.0
P3.7
ACC.2
05
Note:
CLR instruction is as same as SETB
i.e.:
CLR
C
;CY=0
But following instruction is only for CLR:
CLR
A
;A=0
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19. DEC
INC
byte
byte
;byte=byte-1
;byte=byte+1
INC
DEC
DEC
R7
A
40H
; [40]=[40]-1
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20. RR – RL – RRC – RLC A
EXAMPLE:
RR
A
RR:
RRC:
C
RL:
RLC:
C
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21. ANL - ORL – XRL
Bitwise Logical Operations:
AND, OR, XOR
EXAMPLE:
MOV
R5,#89H
ANL R5,#08H
CPL
A
Example:
MOV
L01: CPL
MOV
ACALL
SJMP
;1’s complement
A,#55H ;A=01010101 B
A
P1,A
DELAY
L01
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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
Scratch pad RAM
30H
2FH
Bit-Addressable RAM
20H
1FH
18H
17H
10H
0FH
08H
07H
00H
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Register Bank 3
Register Bank 2
Stack) Register Bank 1)
Register Bank 0

23. Example:
MOV
MOV
MOV
PUSH
PUSH
PUSH
R6,#25H
R1,#12H
R4,#0F3H
6
1
4
0BH
0BH
0BH
0BH
0AH
0AH
0AH
0AH
F3
09H
09H
09H
12
09H
12
08H
08H
08H
25
08H
25
Start SP=07H
25
SP=08H
SP=09H
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SP=08H

24. LOOP and JUMP Instructions
Conditional Jumps :
JZ
Jump if A=0
JNZ
Jump if A/=0
DJNZ
Decrement and jump if A/=0
CJNE A,byte
Jump if A/=byte
CJNE reg,#data
Jump if byte/=#data
JC
Jump if CY=1
JNC
Jump if CY=0
JB
Jump if bit=1
JNB
Jump if bit=0
JBC
Jump if bit=1 and clear bit
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25. DJNZ:
Write a program to clear ACC, then
add 3 to the accumulator ten time
Solution:
AGAIN:
MOV
MOV
ADD
DJNZ
MOV
A,#0
R2,#10
A,#03
R2,AGAIN ;repeat until R2=0 (10 times)
R5,A
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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 00FFH is divided into forward and backward jumps, that is ,
within -128 to +127 bytes of memory relative to the address
of the current PC.
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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.
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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
MOV R1,#59h
MOV R2,#10
L1: MOV A,@R0
MOV @R1,A
INC R0
INC R1
DJNZ R2,L1
; source pointer
; dest pointer
; counter
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29. Decimal Addition
156 + 248
.
100's
10's
1's
.
1
5
6
+
2
4
8
=
4
0
4
16 Bit Addition
1A44 + 22DB = 3D1F
.
256's
16’s
1's
.
1
A
4
4
+
2
2
D
B
=
3
D
1
F
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30. Performing the Addition with 8051
.
256's
1's
.
R6
R7
+
R4
R5
R2
R3
=
65536's
R1
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.
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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
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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
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33. Timer & Port Operations
• Example:
Write a program using Timer0 to create a 10khz square
wave on P1.0
LOOP:
MOV TMOD,#02H
MOV TH0,#-50
SETB TR0
JNB TF0, LOOP
CLR TF0
CPL P1.0
SJMP LOOP
END
;8-bit auto-reload mode
;-50 reload value in TH0
;start timer0
;wait for overflow
;clear timer0 overflow flag
;toggle port bit
;repeat
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34. Interrupts
1. Enabling and Disabling Interrupts
2. Interrupt Priority
3. Writing the ISR (Interrupt Service
Routine)
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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.
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36. Interrupt Vectors
Interrupt
Vector Address
System Reset
0000H
External 0
0003H
Timer 0
000BH
External 1
0013H
Timer 1
001BH
Serial Port
0023H
Timer 2
002BH
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37. Writing the ISR
Example:
Writing the ISR for Timer0 interrupt
T0ISR:
MAIN:
ORG 0000H ;reset
LJMP MAIN
ORG 000BH ;Timer0 entry point
.
;Timer0 ISR begins
.
RETI
;return to main program
.
;main program
.
.
END
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38. Structure of Assembly language
and Running an 8051 program
EDITOR
PROGRAM
Myfile.asm
ASSEMBLER
PROGRAM
Myfile.lst
Other obj file
Myfile.obj
LINKER
PROGRAM
OH
PROGRAM
Myfile.hex
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39. Examples of Our Program Instructions
• MOV C,P1.4
JC LINE1
• SETB P1.0
CLR P1.2
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40. 8051 Instruction Set
ACALL: Absolute Call
JC: Jump if Carry Set
PUSH: Push Value Onto Stack
ADD, ADDC: Add Acc. (With Carry)
JMP: Jump to Address
RET: Return From Subroutine
AJMP: Absolute Jump
JNB: Jump if Bit Not Set
RETI: Return From Interrupt
ANL: Bitwise AND
JNC: Jump if Carry Not Set
RL: Rotate Accumulator Left
CJNE: Compare & Jump if Not Equal
JNZ: Jump if Acc. Not Zero
RLC: Rotate Acc. Left Through Carry
CLR: Clear Register
JZ: Jump if Accumulator Zero
RR: Rotate Accumulator Right
CPL: Complement Register
LCALL: Long Call
RRC: Rotate Acc. Right Through Carry
DA: Decimal Adjust
LJMP: Long Jump
SETB: Set Bit
DEC: Decrement Register
MOV: Move Memory
SJMP: Short Jump
DIV: Divide Accumulator by B
MOVC: Move Code Memory
SUBB: Sub. From Acc. With Borrow
DJNZ: Dec. Reg. & Jump if Not Zero
MOVX: Move Extended Memory
SWAP: Swap Accumulator Nibbles
INC: Increment Register
MUL: Multiply Accumulator by B
XCH: Exchange Bytes
JB: Jump if Bit Set
NOP: No Operation
XCHD: Exchange Digits
JBC: Jump if Bit Set and Clear Bit
ORL: Bitwise OR
XRL: Bitwise Exclusive OR
POP: Pop Value From Stack
Undefined: Undefined Instruction
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41. THANKS
www.techno
groovy.com,
Cell- +917500347448
, +917533940322
www.techno
groovy.com,
Cell- +917500347448
, +917533940322
www.techno
groovy.com,
Cell- +917500347448
, +917533940322
www.techno
groovy.com,
Cell- +917500347448
, +917533940322
www.technogroovy.com, Cell- +91-
www.techno
groovy.com,
Cell- +917500347448
, +917533940322