Pic16f877xa instruction system (assembly language)

Macro understanding

Core mnemonic
Mnemonic symbol      Functional specifications      English full name
ADD     Add up     add
SUB     Subtracting the     substract
RL     Cyclic shift to the left     rotate left
RR     Cycle moves to the right     rotate right
AND     And     and
IOR     or     inclusive or
XOR     Exclusive or     exclusive or
COM     Take the opposite     complement
INC     Add 1    increase
DEC     reduce 1    decrease
MOV     delivery     move
CLR     Zero clearing     clear
RET     return     return
BTF     Bit test     bit test
Instruction system supplementary character description
character      Functional specifications      English full name
W     Working register （ I.e. accumulator ）    -
f     Register address （ take 7 Bit register address ,00H~7FH）    -
b    8 Bit register f Internal address （0~7）    bit
K     Count now （8 Bit constant or 11 Bit address ）、 Constant or label     -
L     The instruction operand contains 8 Immediately K    -
d     Destination address selection ：d=0, Results to W;d=1, Results to f    destination
FSZ     register f by 0, Then jump between     skip if 0
FSC     register f Of b Position as 0, Then jump between     skip if clear
FSS     register f Of b Position as 1, Then jump between     skip if set
( )     Represents the contents of a register     -
(( ))     Indicates the contents of register indirection     -
→     Indicates that the operation result is sent to the target register     -
Examples of common instructions
Chip manual

Register plus 1 Instructions ：INCF
【 Format 】 INCF F,d

【 function 】 register F Add 1

【 explain 】

（1）INCF yes Increment F Abbreviation ;

（2） stay PIC series 8 Bit MCU , Common symbols F Represents various registers and F Serial number address of ;

（3）d＝0 when , The result is deposited in W;d＝1 when , The result is deposited in F.

【 example 】

INCF    PORTC,1    ; take PORTC Add 1
Register minus 1 Instructions ：DECF
【 Format 】 DECF F,d

【 function 】 register F reduce 1

【 explain 】

（1）DECF yes Decrement F Abbreviation ;

（2）d＝0 when , The result is deposited in W;d＝1 when , The result is deposited in F.

【 example 】

ENCODER     EQU 0X21
 
            ……
 
            DECF     ENCODER,1 ; take ENCODER reduce 1
Register reset instruction ：CLRF
【 Format 】 CLRF F

【 function 】 Register clear

【 explain 】

（1）CLRF yes Clear F Abbreviation ;

（2）F The register is cleared to all 0, Make the status bit Z＝1.

【 example 】

CLRF    TRISC       ; Yes TRISC Zero clearing
W Clear command ：CLRW
【 Format 】 CLRW

【 function 】 register W Zero clearing

【 explain 】

（1）CLRW yes Clear W Abbreviation ;

（2）W by PIC Working register of single chip microcomputer ;

（3）W The register is cleared to all 0, Make the status bit Z＝1.

【 example 】

CLRW        ;W＝00H
F Register transfer instruction ：MOVF
【 Format 】 MOVF F,d

【 function 】 take F Register contents are transferred to F or W

【 explain 】

（1）MOVF yes Move F Abbreviation ;

（2） When d＝1 when , to F In itself ; When d＝0 when , to W;

（3） Affect status bits Z

【 example 】

MOVF       PORTB,0    ;PORTB Oral content delivery W
 
MOVWF      PORTA　    ;W The content is PORTB Oral content delivery PORTA
W Register transfer instruction ：MOVWF
【 Format 】 MOVWF F

【 function 】 W Register transfer

【 explain 】

（1）MOVWF yes Move W to F Abbreviation ;

（2） take W Register content transfer F,W The content remains the same ;

（3） Does not affect the status bit .

【 example 】

MOVLW   0x0B        ; send 0BH send W
 
MOVWF   PORTB       ; send W Content to PORTB mouth
Incremental jump instruction ：INCFSZ
【 Format 】 INCFSZ F,d

【 function 】 Incremental jump

【 explain 】

（1）INCFSZ yes Increment F,Skip if 0 Abbreviation ;

（2）F Add... To the contents of the register 1 after , When d＝1 When the result is saved F, When d＝0 I'll deposit it in W;

（3） If the result is 0 Skip the next instruction , Otherwise, execute in sequence ;

（4） Affect status bits Z.

【 example 】

LOOP   INCFSZ     COUNT1,1   ;COUNT1 Add 1, The results are stored in COUNT1
 
       GOTO       LOOP　     ; The result is not zero , loop
 
       MOVWF      COUNT2     ; When the result is zero , Execute the statement
Decrement jump instruction ：DECFSZ
【 Format 】 DECFSZ F,d

【 function 】 Decrement jump

【 explain 】

（1）DECFSZ yes Decrement F,Skip if 0 Abbreviation ;

（2）F Register contents minus 1, The result is deposited in F In itself （d＝1） or W（d＝0）;

（3） If the result is 0 Skip the next instruction , Otherwise, execute in sequence ;

（4） Affect status bits Z;

（5） In actual instructions , When d=1 when , This item is often omitted .

【 example 】

DELAY   MOVLW    25          ; Delay subroutine
 
        MOVWF    N           ; to N assignment 25
 
        LOOP     DECFSZ N,1  ;N-1 Return N And judge the result ＝0？ yes ！ Out of the loop
 
        GOTO     LOOP        ; no ！ Cycle back
 
        RETURN               ; return
Bit clear instruction ：BCF
【 Format 】 BCF F,B

【 function 】 Positional clarity 0

【 explain 】

（1）BCF yes Bit Clear F Abbreviation ;

（2） Symbol B It means something in the film 8 Bit data register F Tag number of ( Or bit address );

（3） The command means ： Set the... Of the register B Positional clarity 0.

【 example 】

BCF     REG1,2     ; Put the register REG1 Of the 2 A reset
Location 1 Instructions ：BSF
【 Format 】 BSF F,B

【 function 】 Location 1

【 explain 】（1）BSF yes Bit Set F Abbreviation ;

（2） Register F Of the B Location 1.

【 example 】

BSF     STATUS,RP0      ; Set the body of the file register 1
The bit test is a zero jump instruction ：BTFSC
【 Format 】 BTFSC F,B

【 function 】 Bit test is 0 Jump

【 explain 】

（1）BTFSC yes Bit Test,Skip if Clear Abbreviation ;

（2） test F The first of the registers B position , if F（B）＝0 Then adjust to the next instruction , Otherwise, execute in sequence .

【 example 】

BTFSC       PORTB,0    ; testing PORTB The second in the mouth 0 Whether a is 0？ yes ！ Skip the next instruction
 
GOTO       CHECK       ; no ！ Then go to the label CHECK The sentence of
 
CALL       DELAY       ;PORTB Of the 0 Is it 1 Then execute the statement directly , Call delay subroutine
Bit test is 1 Jump instruction ：BTFSS
【 Format 】 BTFSS F,B

【 function 】 Bit test bit 1 Jump instruction

【 explain 】

（1）BTFSS yes Bit Test F,Skip if Set Abbreviation ;

（2） test F The first of the registers B position , if F（B）＝1, Then jump to the next instruction , Otherwise, execute in sequence .

【 example 】

BTFSS       PORTB,0     ; testing PORTB The second in the mouth 0 Whether a is 1？ yes ！ Skip the next instruction
 
GOTO        CHECK       ; no ！ Then go to the label CHECK The sentence of
 
CALL        DELAY       ;PORTB Of the 0 Is it 1 Then execute the sentence directly , Call delay subroutine
Constant transfer instruction ：MOVLW
【 Format 】 MOVLW K

【 function 】 Constant transfer

【 explain 】（1）MOVLW yes Move literal to W Abbreviation ;

（2） take 8 Bit immediate is transferred to W register ,k It's a constant 、 Immediate number and label ;

（3） Does not affect the status bit

【 example 】

MOVLW       0x1E    ; constant 30 send W
Subroutine call instruction ：CALL
【 Format 】 CALL K

【 function 】 Subroutine call

【 explain 】

（1）CALL yes CALL subroutine Abbreviation ;

（2）K Is the immediate address ;

（3） Does not affect the status bit .

【 example 】

CALL    DELAY         ; Call delay subroutine
 
DELAY   ……            ; Delay subroutine DELAY
 
        ……
 
        RETURN
An unconditional jump order ：GOTO
【 Format 】 GOTO K

【 function 】 Jump unconditionally

【 explain 】

（1）GOTO yes Go to address Abbreviation ;

（2） Directive K, It is often associated with the label in the program ;

（3） Does not affect the status bit .

【 example 】

STOP    GOTO    STOP    ; Loop execution GOTO sentence , So as to stop
Subroutines return instructions ：RETURN
【 Format 】 RETURN

【 function 】 Subprogram return

【 explain 】

（1）RETURN yes Return from Subroutine Abbreviation ;

（2） Pop up the contents of the cell at the top of the stack and send them to PC, So as to return to the breakpoint of the main program ;

（3） Does not affect the status bit .

【 example 】

SUB  MOVLW   01H     ; Subroutines
 
     ……
 
     RETURN          ; Subprogram return
Empty operation instruction ：NOP
【 Format 】 NOP

【 function 】 Empty operation

【 explain 】

（1）NOP yes No Operation Abbreviation ;

（2） No action generated , Only make PC Add 1, Consume an instruction cycle NOP;

（3） Does not affect the status bit .

【 example 】

MOVLW       0xOF　　    ; send OFH To W
　　　　
MOVWF       PORTB       ;W Content write B mouth
　　　　 
NOP　　　　　            ; Empty operation
 
MOVF        PORTB,W     ; Read operations
Examples of commonly used pseudo instructions
Symbolic name assignment pseudo instruction ：EQU
【 Format 】 Symbol name EQU nn

【 function 】 Symbol name assignment

【 explain 】

（1） Assign a value to a symbol name or register , Once the symbol name is set by EQU assignment , Its value cannot be redefined ;

（2）nn Is a binary value with different length .

【 example 】

COUNT       EQU     100     ; Definition COUNT Constant 100
Program start address pseudo instruction ：ORG
【 Format 】 ORG nnnn

【 function 】 Program start address

【 explain 】

（1） Used to specify the starting address of the source program after the pseudo instruction , That is, the first address of the assembled machine code object program stored in the program memory of the single chip microcomputer ;

（2）nnnn It's a 13 Is a long address parameter .

【 example 】

ORG 0x00     ; The program assembly address is from 00H Start
Program end pseudo instruction ：END
【 Format 】 END

【 function 】 Program end

【 explain 】

（1） Pseudo instruction at the end of instruction END Is the notification assembler MPASM End the assembly of the source program , Even if there are statements after , And no longer compile ;

（2） In a source program, there must be END Pseudo instruction ;

（3） There can only be one END;

（4） At the end of the whole program .

【 example 】 Use directly at the end of the program , This ends the program

Call in external function pseudo instruction ：INCLUDE
【 Format 】 INCLUDE “ file name ”

【 function 】 Call in external functions

【 explain 】

（1） Used to tell the assembler , Include a pre compiled external program file , As part of this source program ;

（2） This can reduce repetitive work , Improve programming efficiency .
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