Share some common syntax and program errors in MCU assembly language

First, assembly software assembly failure reasons analysis Here using the Keil C51 software package macro assembler A51 as a compiler, MCU assembly language should pay attention to certain grammar when writing, detailed introduction can refer to the relevant reference books, grammar errors will cause assembly Failure, common assembly errors are as follows:
1. Repeating labels: It is common to forget to modify the label when copying and pasting the program, causing multiple identical labels to appear. The labels are not allowed to be repeated.
2. Punctuation is entered in full-width mode: The assembler requires punctuation in half-width mode, otherwise assembly fails. You can switch to half-width mode when you type:,; or enter punctuation in uppercase, which is a mistake that is easy to make and not easy to detect.
3. Value #FFH before omission 0: According to the requirement, add 0 before a~f, write #0FFH
4. The letter O and the number 0 are confused: Sometimes these two words look exactly the same, pay attention to ~~
5. Missing ":" after the label
6. The label uses special characters: The label cannot use the instruction mnemonic, pseudo instruction, special function register name and "#", "@" used in the command system of 8051, the length is 2~6 characters, the first The letters must be English letters. For example, the characters T1, T2, A, and B have specific meanings and are not allowed for labels.
7. AJMP jumps over 2K address: AJMP is a short jump command with a 2K address range limit.
8. Exceeded address range: JB P3.2, EXIT jumps over -128 to 127 address ranges. This is the most prone error! You may be able to compile and compile successfully. If you add a program, the program will prompt an error. You can convert JB P3.2, EXIT to JNB P3.2, LD01 AJMP EXIT. LD01: AJMP EXIT ......
9. The letter I and the number 1 are confused: The common problem of daredevil.
10. Create an assembly language instruction that does not exist in the invention: This innovation is not welcome in the process of writing a program. This instruction assembler does not support it, and the chip does not recognize it.
11. The symbol ":" ";" is best written in half-width.

Second, the program is wrong
1. Register repeated call: For example, R4=5 is set in the main program, which means that the main program loops 5 times, and one of the delay subroutines uses R4, which makes the value of R4 disorder, causing the program to fail to execute normally. .
2. Unfamiliar hardware: The single-chip microcomputer generally uses pull-down output, and often the port output 0 drives the peripheral work. Contrary to the common positive logic, it is easy to make mistakes.
Third, the instruction system commonly used symbols and meanings
(1) Ri: Working register 0 and working register 1, i=0 or 1. That is, R0~R1.
(2) Rn: Working registers R0 to R7, n=0 to 7.
(3) @Ri: Register Ri indirectly addresses 8-bit memory cells 00H to FFH.
(4) direct: 8-bit direct address, which can be 80H to FFH of internal RAM 00H to 7FH or SFR.
(5) #data: 8-bit immediate.
(6) #data16: 16-bit immediate.
(7) addr16: 16-bit destination address. Used for LCALL and LJMP instructions, can be called or transferred anywhere in the 64K program memory space. (8) addr11: 11-bit destination address. Used for ACALL and AJMP instructions, which can be called or transferred within the 2K byte page where the next instruction address is located.
(9) rel: A signed 8-bit offset address for SJMP and all conditional branch instructions. The range is -128 to +127 bytes with respect to the address of the first byte of the next instruction.
(10) DPTR: Data pointer, which can be used as a 16-bit address register.
(11) bit: bit address. Bit addressable in on-chip RAM and addressable bits in SFR.
(12) A: Accumulator Acc.
(13) B: General purpose registers, mainly used in multiplication MUL and division DIV instructions.
(14) Cy: Carry flag or accumulator in the Boolean processor.
(15) @: The prefix of the indirect register or base register. Such as @Ri, @DPTR, @A+PC, @A+DPTR. The advice of writing assembly language should develop good programming habits, such as label alignment, parameter alignment, and annotation alignment, which are pleasing to the eye and not easy to make mistakes. The label is preferably in meaningful English, which is more intuitive, the annotation is as detailed and accurate as possible, easy to read later, and is useful for calling as a subroutine module in other programs. Also pay attention to the accumulation of typical program modules, and then the complex program is also composed of a small program module, in the initial stage can be written for typical programs such as: delay subroutine, table lookup subroutine, button debounce subroutine, etc. Practice once, so impressed, easy to quote later.

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