preface

With the deepening of development, the research on assembly instructions also needs to continue, mainly the analysis of assembly examples and the detailed explanation of instructions.
Then, there is a very serious problem. That is how to learn assembly code. I believe different people have different solutions, but for me, or most embedded, bottom-level or driver developers, they start with c language as their learning track. Then I also recommend a learning method, that is, from c to grey assembly, and then from assembly to c, It is also a good habit to learn new skills through the skills you have mastered.

Tip: the following is the main content of this article. The following cases can be used for reference

1, What is assembly:

In fact, it is impossible for our machine to recognize what high-level languages such as c we write. Only machine language can be recognized, and assembly language is a kind of machine language. However, assembly language can help us understand through mnemonics and other symbols. Therefore, some developers use this language for programming.

2, Example:

This is a typical example of storage and writing in official documents. I will use this example to study it in detail.

; assembly language ;Indicates the beginning of a comment

; This write routine assumes the following:
; 1. The 16 bytes of data are loaded, starting at the address in DATA_ADDR
; 2. Each word of data to be written is made up of two adjacent bytes in DATA_ADDR,
; stored in little endian format
; 3. A valid starting address (the least significant bits = 000) is loaded in ADDRH:ADDRL
; 4. ADDRH and ADDRL are located in shared data memory 0x70 - 0x7F
;
BCF INTCON,GIE ; 					Disable ints so required sequences will execute properly
BANKSEL EEADRH  ;					 Bank 3
MOVF ADDRH,W  ; Load initial address
MOVWF EEADRH  ;
MOVF ADDRL,W  ;
MOVWF EEADRL  ;
MOVLW LOW DATA_ADDR ; Load initial data address
MOVWF FSR0L  ;
MOVLW HIGH DATA_ADDR ; Load initial data address
MOVWF FSR0H  ;
BSF EECON1,EEPGD  ; Point to program memory
BCF EECON1,CFGS  ; Not configuration space
BSF EECON1,WREN  ; Enable writes
BSF EECON1,LWLO  ; Only Load Write Latches
LOOP
MOVIW FSR0++  ; Load first data byte into lower
MOVWF EEDATL  ;
MOVIW FSR0++  ; Load second data byte into upper
MOVWF EEDATH  ;
MOVF EEADRL,W  ; Check if lower bits of address are '000'
XORLW 0x07  ; Check if we're on the last of 8 addresses
ANDLW 0x07  ;
BTFSC STATUS,Z  ; Exit if last of eight words,
GOTO START_WRITE  ;
MOVLW 55h  ; Start of required write sequence:
MOVWF EECON2  ; Write 55h
MOVLW  0AAh  ;
MOVWF EECON2  ; Write AAh
BSF EECON1,WR  ; Set WR bit to begin write
NOP  ; Any instructions here are ignored as processor
; halts to begin write sequence
NOP  ; Processor will stop here and wait for write to complete.
; After write processor continues with 3rd instruction.
INCF EEADRL,F  ; Still loading latches Increment address
GOTO LOOP  ; Write next latches
START_WRITE
BCF EECON1,LWLO  ; No more loading latches - Actually start Flash program
; memory write
MOVLW  55h  ; Start of required write sequence:
MOVWF EECON2  ; Write 55h
MOVLW 0AAh  ;
MOVWF EECON2  ; Write AAh
BSF EECON1,WR  ; Set WR bit to begin write
NOP  ; Any instructions here are ignored as processor
; halts to begin write sequence
NOP ; Processor will stop here and wait for write complete.
; after write processor continues with 3rd instruction
BCF EECON1,WREN  ; Disable writes
BSF INTCON,GIE ; Enable interrupts

Example: pandas is a NumPy based tool created to solve data analysis tasks.

3, Instruction

In contrast, the pic instruction set is relatively small. Here is the instruction set of PIC16F1823, and then I list some simple and complex instructions

1. Simple instructions

;bcf Instruction: this instruction is actually clearing the register f The first b position
BCF Bit Clear f
BCF f,b
Operands: 0 <f < 127
0 <b <7
Operation: 0 -> (f<b>)
Status Affected: None
Description: Bit 'b' in register 'f' is cleared.

;MOVF Instruction: this instruction is actually to f Move the contents of the register to d in

 MOVF f,d
Operands: 0 <f < 127
d ->[0,1]
Operation: (f) < (dest)
Status Affected: Z
Description: The contents of register f is moved to
a destination dependent upon the
status of d. If d = 0, destination is W
register. If d = 1, the destination is file
register f itself. d = 1 is useful to test a
file register since status flag Z is
affected.
Words: 1
Cycles: 1
Example: MOVF FSR, 0
After Instruction
W = value in FSR register
Z = 1

2. Complex instructions

RRF instruction:

summary

In short, this article is actually to explain some compilation knowledge