Bài giảng The 8051 Microcontroller - Chapter 4: Instruction set how to write a program - Lê Chí Thông
ĐH Bách Khoa - ĐHQG TP.HCM
Lê Chí Thông - [email protected]
The 8051 Microcontroller
Chapter 4
Instruction Set
How to write a program
Lê Chí Thông
sites.google.com/site/chithong
Ho Chi Minh City University of Technology
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Chapter 4
1. Addressing Modes
2. Instruction Set
3. How to write a program
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ĐH Bách Khoa - ĐHQG TP.HCM
Lê Chí Thông - [email protected]
1. Addressing Modes
•
•
•
•
•
•
•
•
Immediate Addressing
Register Addressing
Direct Addressing
Indirect Addressing
Relative Addressing
Absolute Addressing
Long Addressing
Indexed Addressing
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Coding format- Addressing modes
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ĐH Bách Khoa - ĐHQG TP.HCM
Lê Chí Thông - [email protected]
Addressing Modes
•
•
•
•
•
•
•
•
Immediate Addressing
Register Addressing
Direct Addressing
Indirect Addressing
Relative Addressing
Absolute Addressing
Long Addressing
Indexed Addressing
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Immediate Addressing
- Source operand is constant
- Use # sign
(Source)
A
0 0 0 0 1 1 0 0
1 1 0 0 0 1 0 0
0 0 0 0 1 1 1 0
MOV
MOV
MOV
ADD
MOV
A,#12
A
A,#0C4H
R1
R1,#1110B
A,#11110001B
DPTR,#2000H
CY
1
A
1 0 1 1 0 1 0 1
DPH 0 0 1 0 0 0 0 0
DPL 0 0 0 0 0 0 0 0
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ĐH Bách Khoa - ĐHQG TP.HCM
Lê Chí Thông - [email protected]
Addressing Modes
•
•
•
•
•
•
•
•
Immediate Addressing
Register Addressing
Direct Addressing
Indirect Addressing
Relative Addressing
Absolute Addressing
Long Addressing
Indexed Addressing
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Register Addressing
R1
0 0 1 1 0 1 1 0
Ex: MOV
R1,#36H
A
0 0 1 1 0 1 1 0
0 0 0 0 1 1 1 1
0 0 0 0 0 1 1 0
MOV
A,R1
R7
A
MOV R7,#0FH
ANL
INC
A,R7
A
A
A
0 0 0 0 0 1 1 1
0 0 0 0 0 1 1 0
DEC
MOV
INC
A
DPTR,#2000
DPTR
(source)
DPH 0 0 1 0 0 0 0 0
DPL 0 0 0 0 0 0 0 1
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Addressing Modes
•
•
•
•
•
•
•
•
Immediate Addressing
Register Addressing
Direct Addressing
Indirect Addressing
Relative Addressing
Absolute Addressing
Long Addressing
Indexed Addressing
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Direct Addressing
• Access internal RAM and SFRs
MOV A,70H
MOV R0,40H
MOV 56H,A
; copy contents of RAM at 70H to A
; copy contents of RAM at 40H to A
; put contents of A into RAM at 56H
MOV 0D0H,A ; put contents of A into PSW
MOV PSW,A ; same
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Direct Addressing vs. Immediate Addressing
≠
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Play with R0-R7 (bank 0) by Direct Addressing
MOV A,04H ≡ MOV A,4 ≡ MOV A,R4
MOV A,07H ≡ MOV A,7 ≡ MOV A,R7
MOV 07H,06H ≡ MOV 7,6 ≠ MOV R7,R6
MOV R2,#5 ; Put 5 in R2
MOV R2,5 ; Put content of RAM at address 5 in R2
MOV R2,5
MOV R2,#5
≠
R2
0 0 0 0 0 1 0 1
R2
05H
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Addressing Modes
•
•
•
•
•
•
•
•
Immediate Addressing
Register Addressing
Direct Addressing
Indirect Addressing
Relative Addressing
Absolute Addressing
Long Addressing
Indexed Addressing
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Indirect Addressing
• The address of the source or destination is specified in registers.
• Use registers R0 or R1 for 8-bit address (internal or external
RAM)
• Use @ sign to access the content of the memory location: @R0,
@R1
Ex: MOV
R0,#30H ;R0 ꢀ 30H
MOV
A,@R0 ;Aꢀ(R0): read content of internal RAM at
; address specified by R0 to A
Internal RAM
R0
A
7FH
30H
00H
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Indirect Addressing – External 8-bit address RAM
Ex: MOV
R0,#30H ;R0 ꢀ 30H
MOVX A,@R0 ;Aꢀ(R0): read content of eXternal RAM at
; address specified by R0 to A
External RAM
R0
A
0 0 1 1 0 0 0 0
30H
00H
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Indirect Addressing – External 16-bit address RAM
• Uses DPTR register for 16-bit addresses (external memory)
• Use @ sign to access the content of the memory location:@DPTR
Ex:
; DPTR ꢀ Address
; read content of external RAM at
address 4000H to A
;
External RAM
DPTR
40H
A
00H
4000H
00H
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Indirect Addressing – External 16-bit address RAM
Ex:
; DPTR ꢀ Address
; write content of A to external RAM
; at address 31FFH
External RAM
DPTR
31H
A
FFH
31FFH
00H
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Register Addressing vs. Indirect Addressing
≠
Internal RAM
R1
7FH
00H
A
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Example of Indirect Addressing
Ex: (Implementation of array)
R0 ꢀ 60H
Clear internal RAM from address
60H to 7FH
(R0) ꢀ 0
MOV R0, #60H
LOOP: MOV @R0, #0
R0 ꢀ R0+1
INC
R0
CJNE R0, #80H, LOOP
N
R0= 80h?
Y
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Your Turn!
Write a program to output (send) the content of internal RAM,
from address 20H to 45H, to Port 1
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Addressing Modes
•
•
•
•
•
•
•
•
Immediate Addressing
Register Addressing
Direct Addressing
Indirect Addressing
Relative Addressing
Absolute Addressing
Long Addressing
Indexed Addressing
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Relative Addressing
• Used in SJMP instruction
• A relative address (or offset) is an 8-bit signed value.
• It is added to PC to form a new value for PC.
• Range: -128 ~ +127
• Usually used with label ☺
Ex: SJMP LABEL1 is in memory
at locations 0100H and 0101H
ꢁ PC = 0102H
If LABEL1 is the label representing
an instruction at location 0107H
ꢁ Relative offset is
0107H – 0102H = 5
ꢁ Opcode of SJMP LABEL1 is 80 05
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Relative Addressing
Ex: SJMP LABEL2 is in memory
at locations 2040H and 2041H
ꢁ PC = 2042H
If LABEL2 is the label representing
an instruction at location 2038H
ꢁ Relative offset is
2038H – 2042H = -10 = F6H
ꢁ Opcode of SJMP LABEL1 is 80 F6
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Your Turn!
Ex:
ORG 0000H
SETB P1.0
NOP
AGAIN:
NOP
CLR P1.0
NOP
SJMP AGAIN
END
a. Find the opcode of SJMP AGAIN instruction?
b. Find the duration of P1.0=1? P1.0=0?
c. What is the result of this program?
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Addressing Modes
•
•
•
•
•
•
•
•
Immediate Addressing
Register Addressing
Direct Addressing
Indirect Addressing
Relative Addressing
Absolute Addressing
Long Addressing
Indexed Addressing
Lê Chí Thông
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Absolute Addressing
• Used in AJMP, ACALL instruction
• Usually used with label ☺
Within any 2K page, the upper five address
bits are the same for the source and
destination addresses.
The lower 11 bits of the destination are
supplied in the instruction
Memory map showing 2K pages
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Addressing Modes
•
•
•
•
•
•
•
•
Immediate Addressing
Register Addressing
Direct Addressing
Indirect Addressing
Relative Addressing
Absolute Addressing
Long Addressing
Indexed Addressing
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Long Addressing
• Used in LCALL and LJMP instruction
• Use full 16-bit address
• Usually used with label ☺
Ex: LCALL SUBPROGRAM1
LJMP
LABEL2
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Addressing Modes
•
•
•
•
•
•
•
•
Immediate Addressing
Register Addressing
Direct Addressing
Indirect Addressing
Relative Addressing
Absolute Addressing
Long Addressing
Indexed Addressing
Lê Chí Thông
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Indexed Addressing
• Base address (PC or DPTR) + Offset (A) ꢁ Effective Address
• Used with JMP or MOVC
Ex: MOVC
MOVC
A, @A+DPTR
A, @A+PC
@A+DPTR
JMP
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Indexed Addressing
Ex: An even number from 0 to 6 is in the Accumulator. The following
sequence of instructions branches to one of four AJMP
instructions in a jump table starting at JMP_TBL.
MOV DPTR, # JMP_TBL
JMP @A + DPTR
JMP_TBL: AJMP LABEL0
AJMP LABEL1
AJMP LABEL2
AJMP LABEL3
• If the Accumulator equals 04H when starting this sequence,
execution jumps to label LABEL2. Because AJMP is a 2-byte
instruction, the jump instructions start at every other address.
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2. Instruction Set
• 255 instructions
1-byte instructions: 139
2-byte instructions: 92
3-byte instructions: 24
• Instruction set summary (pdf)
• Full instruction set (pdf)
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Instruction Types
• Data transfer
• Arithmetic
• Logical
• Boolean variable
• Program branching
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8051 Instruction Set Summary
Legend
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8051 Instruction Set Summary
Data Transfer
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8051 Instruction Set Summary
Data Transfer
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Data Transfer
MOV dest, source
; dest ꢀ source
MOV A,#72H
MOV R4,#62H
MOV B,0F9H
;A=72H
;R4=62H
;B=the content of address F9H of RAM
MOV DPTR,#7634H
MOV DPL,#34H
MOV DPH,#76H
MOV P1,A
;move (out) A to Port 1
≠ MOV A,72H
Note 1:
MOV A,#72H
Note 2:
MOV A,R3 ≡ MOV A,3 ;R3 of bank 0 is location 3
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Instruction Types
• Data transfer
• Arithmetic
• Logical
• Boolean variable
• Program branching
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8051 Instruction Set Summary
Arithmetic Operations
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8051 Instruction Set Summary
Arithmetic Operations
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