8051 Assembly Language

1. 8051 Assembly Language
Dr. Noorullah Shariff

2. Outline
• 8051 Programmer’s Model
• Addressing Modes
• Data Movement Instructions
• Arithmetic Instructions
• Logical Instructions
• Shift Instructions
• Bit Manipulation
• Program Control Instructions
Dr. Noorullah Shariff

3. 8051 Introduction
• 8 bit Data bus, 16 bit Address bus
• Many Special Function Registers (SFRs) for
control and I/O
Dr. Noorullah Shariff

4. 8051 Programmer’s Model (1)
Program Memory
OR
FFFF
0000
FFFF
0000
1000
0FFF
if EA = 1 if EA = 0
• All instructions
• Constant Data
(Using MOVC)
64 K
External
60 K
External
4 K
Internal
0
7
7
0
Data Memory
SFRs
RAM
80
FF
00
7F
AND
Direct
Direct , Register,
Reg. Indirect
FFFF
0000
64 K
External
(Using MOVX)
@R
@DPTR
Internal
Dr. Noorullah Shariff

5. 8051 Programmer’s Model (2)
Port 0
Stack pointer
Data pointer DPTR
Power Control
timer/counter control
timer/counter Mode
timer 0 Low
timer 1 Low
timer 0 High
timer 1 High
Port 1
Serial Control
Serial Data Buffer
Port 2
Interrupt Enable Ctr 1* IE
* P2
SBUF
* SCON
* P1
* TH1
* TH0
* TL1
* TL0
TMOD
* TCEN
PCON
DPH
DPL
SP
* P080
81
82
83
87
88
89
8A
8B
8C
8D
90
98
A0
99
A8
* P3
* IP
* PSW
* ACC
* BF0
FF
E0
D0
B8
B0
SFRs
SFRs 7F
00
08
10
18
20
30
Scratch Pad Area
RAM
Bit Addressable RAM
Bank 3
Bank 2
Bank 1
Bank 0
R0
R7
R0
R7
R0
R7
R0
R7
Select Bank
with
PSW.4 , .3 =
RS1, RS0
Bit #00 7F OR
20.0 2F.7
* = Bit Addressable
Dr. Noorullah Shariff

6. 8051 Addressing Modes (1)
• Immediate - # Label or Number
MOV R6,#14 ; R6 14 10
MOV A,#0CAh ; Acc CA 16
MOV DPTR,#loc ; DPTR value of symbol “loc”
• Direct - Label or Number
MOV PSW,R5 ; M(PSW) R5
MOV A,045h ; Acc M(45 10)
• Register - Rn
MOV R1,A ; R1 Acc
MOV B,R3 ; B R3
Dr. Noorullah Shariff

7. 8051 Addressing Modes (2)
• Register Indirect - @R0, @R1, @DPTR
MOV @R0,#250 ; M(R0) 250 10
MOV A,@R1 ; A M(R1)
MOVX @DPTR,A ; External data M(DPTR) A
• Register Indirect Indexed - @A+DPTR, @A+PC
MOVC A,@A+DPTR ; A ROM(A+DPTR)
MOVC A,@A+PC ; A ROM(A+PC)
JMP @A+DPTR ; PC (A+DPTR)
• Bit - bit number or label.bit or bit label
MOV C,IE.0 ; CY bit 0 of IE reg (EX0)
MOV C,EX0 ; same
SETB 07Fh ; Bit 7F 1
SETB 2F.7 ; same
Dr. Noorullah Shariff

8. 8051 Instructions
• Instruction Classes
– Data Movement
– Arithmetic
– Logical
– Shift
– Bit Manipulation
– Program Control
Dr. Noorullah Shariff

9. 8051 Data Movement - 1
MOV R, # Rn
D
A
MOVE
MOV A, # A Immediate
D A Direct
R A Register
@R A Register Indirect
MOV D, # Direct
D
R
@R
A
MOV @R, # Register Indirect
D
ADr. Noorullah Shariff

10. 8051 Data Movement - 2
• Move External Data RAM
MOVX A, @R
A, @DPTR
MOVX @R, A
@DPTR, A
Move From Program Memory
MOVC A, @A+DPTR Acc Rom(A+DPTR)
A, @A+PC Acc Rom(A+PC)
Others
PUSH D SP SP+1, m(SP) D
POP D D m(SP), SP SP - 1
XCH A, R SWAP Acc Rn
D
@R
Dr. Noorullah Shariff

11. 8051 Arithmetic - 1
ADDC A, # Acc A+Immediate+Carry
D
R
@R
Add/Subtract
ADD A, # Acc A+Immediate
D
R
@R
SUBB A, # Acc Acc-Immediate-Carry
D
R
@R
Dr. Noorullah Shariff

12. 8051 Arithmetic - 2
Inc/Dec
INC A Acc Acc+1
D
R
@R
DEC A Acc Acc-1
D
R
@R
Mul/Div
MUL AB B:A Acc * B (unsigned)
DIV AB A Quo ( A/B ) (unsigned)
B Rem( A/B )
Dr. Noorullah Shariff

13. 8051 Logical
• Other
CLR A Acc 0
CPL A Acc Acc
SWAP A Acc(7-4) Acc(3-0)
AND,OR,XOR
AND A, #
ORL D
XRL R
@R
D, A
D, #
Dr. Noorullah Shariff

14. 8051 Shift
Rotates
RL A
RLC A
RR A
RRC A
Acc
7 0
Acc
7 0
C
Acc
7 0
Acc
7 0
C
Dr. Noorullah Shariff

15. 8051 Bit Manipulation - 1
Clear/Set/Complement
CLR C Carry 0
bit bit 0
SETB C
bit
CPL C
bit
And, Or, Move
ANL C, bit Carry Carry AND bit
C, /bit Carry Carry AND bit
ORL C, bit
C, /bit
MOV C, bit
bit, C
Dr. Noorullah Shariff

16. 8051 Bit Manipulation - 2
Jump
JC label Jump if Carry set
JNC label Jump if Carry clear
JB bit, label Jump if bit set
JNB bit, label Jump if bit clear
JBC bit, label Jump if bit set, then clear bit
label = PC relative (+ 127)
Dr. Noorullah Shariff

17. 8051 Program Control - 1
Jump
AJMP label-A Absolute Jump- 11 bits(2K)
LJMP label-L Long Jump - 16 bits (64K)
SJMP label Short Jump
JMP @A+DPTR Jump Indirect PC (A+DPTR)
JZ label Jump if zero
JNZ label Jump if not zero
Compare and Jump
CJNE A, #, label Compare 1st
op to 2nd
op and
A, D, label jump to label if not Equal
R, #, label
@R,#, label
Dr. Noorullah Shariff

18. 8051 Program Control - 2
Decrement and Jump
DJNZ R, label Rn = Rn-1 , Jump if not zero
D, label
Subroutines
ACALL label-A Absolute Call - 11 bits (2K)
LCALL label-L Long Call - 16 bits (64K)
RET Return from Subroutine
RETI Return from ISR
PC m(SP), SP SP-2
Dr. Noorullah Shariff

19. example of delay
mov a,#0aah
Back1:mov p0,a
lcall delay1
cpl a
sjmp back1
Delay1:mov r0,#0ffh;1cycle
Here: djnz r0,here ;2cycle
ret ;2cycle
end
Delay=1+255*2+2=513 cycle
Delay2:
mov r6,#0ffh
back1: mov r7,#0ffh ;1cycle
Here: djnz r7,here ;2cycle
djnz r6,back1;2cycle
ret ;2cycle
end
Delay=1+(1+255*2+2)*255+2
=130818 machine cycle

20. Long delay Example
GREEN_LED: equ P1.6
org ooh
ljmp Main
org 100h
Main: clr GREEN_LED
Again: acall Delay
cpl GREEN_LED
sjmp Again
Delay: mov R7, #02
Loop1: mov R6, #00h
Loop0: mov R5, #00h
djnz R5, $
djnz R6, Loop0
djnz R7, Loop1
reset service
main program
subroutine

21. Example Programs: 1

22. Example Programs: 2

23. Example Programs: 2

24. Example Programs: 3
Method 2 : Since the number is the same for each register, put the number in A
and MOV A to each register.

25. Example Programs: 4

26. Example Programs: 4 Continued