Pic Single-Chip assembly language learning (I.)

1, assembly language statement format:

Designator opcode (instruction mnemonic) operand;
(label) (opcode) (operand) (comment)

2. Common pseudo-directives

a.equ--Symbol name Assignment pseudo-directive
Format: symbol name Equnn

b.org--program start address define pseudo-directives
Format: orgnnnn

c.end--program end pseudo-directive
Format: END

d.list--List option pseudo-directive
Format: LIST [optional, Options, ...]

E.include: Transfer into external program file pseudo-directive
Format: INCLUDE "file name"

2. Branch program Structure

--A few notes about the application of the instructions in the program:
(1) All logical operations (with, or, XOR) and arithmetic operations (plus, minus) that require 2 numbers of participants need to be placed in W in advance. For the use of the subtraction command more attention, should be pre-placed in the "W," or "pre-put" in the number of W, in the operation as a meiosis, and the number of registers as a meiosis.
(2) A conditional jump instruction often needs to follow an unconditional jump instruction, in order to achieve long-distance transfer and the branch of the program.
(3) pic Microcontroller instruction system is not set up a dedicated stop instruction, you can use a jump to their own unconditional jump instruction Goto to achieve.

3. PIC microcontroller directive

Consists of 3 basic types of directives:
A. Byte manipulation class directives
B. bit operation class Instruction
C. Immediate count and control operation class directives

For byte Operations directive,f--> file Register identifier,d--> target Register identifier

Description: The target identifier specifies where the operation results are stored:
D=0 operation result deposited W Register
D=1 operation result is stored in the specified file register, d default value is 1

4. Instruction Set

5. Example

1;--------------------------------------------------------2 3 ; Sequential program Structure4 , 20H Unit low 4-bit out of 21H, high four-bit out of deposit to 22H5 ; key points: ANDLW and Swapf6 7;---------------------------------------------------------8MOVF 20H,0to send the contents of a 20H unit to a person W9 ANDLW 0FH; W high four-bit clear 0 low 4-bit remains unchangedTen MOVWF 21H; send the lower 4 bits after splitting to 21H OneSwapf 20H,0the 20H unit content is high and the low half byte is swapped and sent W A  - ANDLW 0FH, then the W high four bits clear 0 low four bits remain unchanged - MOVWF 22H; Send the split high four bits to the 22H unit the  -  -;-------------------------------------------------------- -  + ; Branch Program Structure - ; 20H and 21H units in RAM hold 2 numbers to find large deposits in 22H units + point: Two number subtraction, judging the value of the flag bit C A  at;--------------------------------------------------------- - status EQU 03H; Define status register address is 03H -C EQU0; Define the rounding/Borrow flag C has an address of 0 in status -MOVF 20H0to send the contents of a 20H unit to a person W -SUBWF 21H0using the contents of the 21H unit minus the contents of W, the result exists in W -BTFSS status,c; if c=1, without borrow, the number in the 21H unit is large, jumping to F21big inGOTO F20big; if c=0, with borrow, the 20H unit is larger, then jumps to F20big -      toF21big movf 21H,0to deposit the contents of 21H into the W register + MOVWF 22H; then dump it to the 22H unit. - GOTO STOP; Skip the following two instructions to the end of the program the          *F20big movf 20H,0to deposit the contents of 20H into the W register $ MOVWF 22H; then dump it to the 22H unit.Panax Notoginseng  - stop GOTO Stop; task complete, stop, stand still the  +  A;-------------------------------------------------------- the  + ; Cyclic program Structure - in the data memory, 50 cells starting from address 30H are all written to 00H $ ; Important: The indirection register FSR as the address pointer $  -;--------------------------------------------------------- - COUNT EQU 20H; Specify the 20H unit as the counter (i.e. loop variable) the FSR EQU 04H; define FSR Register address of 04H - indf EQU 00H; set INDF register address is 00HWuyi MOVLW D50; the counter initial value 50 is fed into W the MOVWF COUNT; then turn 50 into the counter (as the operating value of the loop variable) - MOVLW 30H; put 30H (start address) into W Wu MOVWF FSR; turn 30H into Register FSR (used as address pointer) -          About NEXT CLRF indf; Clear 0 of the units specified with the FSR content as addresses $INCF FSR,1address pointer content plus 1, pointing to the next cell -Decfsz COUNT,1, the count is reduced by 1, and the result is 0. Skip to the next instruction to stop - Goto next; Jump back and perform the next loop - stop GOTO Stop; Execute the statement after the loop is completed to achieve downtime A  +;-------------------------------------------------------- the  - ; sub-Program Structure $ 3-digit maximum is placed in a 40H unit the  the;--------------------------------------------------------- the STATUS EQU 03H the C EQU 00H - X EQU 20H in Y EQU 21H the Z EQU 22H the;-------------------------------------------------------- About  the ; Main program the  the;--------------------------------------------------------- +  -MAIN movf 30H,0 the MOVWF XBayiMOVF 21H,0 the MOVWF Y the Call SUB -MOVF Z,0 - MOVWF X theMOVF 32H,0 the MOVWF Y the Call SUB theMOVF Z,0 - MOVWF 40H the Stop GOTO Stop the;-------------------------------------------------------- the 94 ; subroutine: (Entry parameters: X and y, exit parameters: Z) the  the;--------------------------------------------------------- theSUB movf X,0to send x content to a person W98SUBWF Y,0        ; Y content minus W content, results are deposited w AboutBTFSS status,c; if c=1, does not occur borrow, executes next, otherwise jumps - GOTO X_big101         102Y_big movf Y,0The data in Y is fed into w103 MOVWF z; and then dump it to Z.104 GOTO theend; Skip the following two to the end the         106X_big movf X,0The data in X is fed into W107 MOVWF z; and then dump it to Z.108TheEND return; sub-program returns

Pic Single-Chip assembly language learning (I.)