What does the instruction IN245 mean in the compilation

out and in are port read and write commands in the assembly. The port is used by the host and the peripherals for data exchange, which is divided into three types: data port, state port and control port For example: in al, 21h means to read a byte of data from the 21h port to al;

in the assembly is the port read operation instruction. in al, 92h indicates that one byte of data is read from port 92h to al;

Assembly language in the 8086 series.

Middle. The In command means to read data from the port, for example, in al, 80h, and read the data from the 80h port into al.

The out command means to output data to the port, e.g. out 80h, al, to output al to the 80h port.

What single-chip microcomputer you use, generally does not have these two instructions. You may need to look at the datasheet of the chip you are using. It's best to post the program and take a look.

Inter-segment jump command, used in x86 real mode. jmp is an intra-segment jump.

jmpi go,0x0c70

go：mov ax，cs

Jump to, 0x0c70:go to execute.

jmpi 0, 09000h

It means an indirect jump (equivalent to jumping to another segment to start execution), that is, the program jumps to 9000:0 to continue executing the program.

--If the current segment is 0 cs == 0jmpi 0, 09000h ; Next execute 9000:0jmp 0; Next, perform a 0:0 reference.

Jump command, which is equivalent to a goto statement.

It is an inter-segment jump command that can be directed to a specified segment address.

JMP is an unconditional jump directive.

Such as ......mov cx,9

jmp m1

m1:…then go to M1 for execution.

Oh, never seen one.

JNZ SHORT 7C921065 means:

Before this sentence, there is a command that affects the zero flag, such as inner cmp or sub....After the sentence is executed, if it is not 0 (zr=0), the command cs:7c921065 is executed.

short is the sign of short transfer, indicating this JNZ SHORT 7C921065 directive.

The distance between CS:7C921065 and CS:7C921065 is within 0ffh.

This command is executed by jumping to the address 7c921065 when the zero flag (zf) is nz. The word short has no special meaning here, so I can ignore it.

cmp ax,bx

jnz short 7c921065

JNZ (Jump If Not Zero Flag Set) and JNE (Jump If Not Equal) have the same effect.

If the previous command is not zero, go to short 7c921065

MCU assembly da a instruction is a decimal adjustment instruction, which is used in conjunction with the addition instruction, and it makes no sense to use it in other occasions and even makes mistakes, such as decimal addition 38+55=93 assembly as mov a, 38h ; a = 38hadd a, #55h ; a = 38h+55h=8dh

da a ;a = 93h after adjusting the instruction is 93

set series of instructions to set the value of the target operand to 0 or 1 based on the status identifier in the eflags register. The target operand points to a byte register, or a byte in memory.

The set family includes a number of directives, which all start with set and are suffix 1-2 characters. All the instructions and usage are given in the official manual, as shown below:

set series commands to perform the following operations:

if condition

then dest ← 1;

else dest ← 0;

If the condition is true, set the target operand to 1, otherwise set it to 0. The conditions are given in parentheses in the description section of the directive. Here's an example:

The first instruction seta with the condition cf=0 and zf=0, if this condition holds, the target operand is set to 1, otherwise it is set to 0.

Decimal Adjust After Addition (DAA).

This instruction is used to adjust the value of AL, which is the result of the ADD or ADC operation of two compressed BCD codes.

The compressed BCD code stores two BCD codes in one byte, and the lower four bits and the upper four bits are all one BCD code.

The rules for its adjustment are as follows:

1. If the lower four digits of al are greater than 9, or the flag digit af=1, then, al=al+6, and af=1 are juxtaposed

2. If the upper four bits of Al are greater than 9, or CF=1, then, AL=AL+60H, and cf=1 are juxtaposed

3. If the above two points are not true, then clear the flag AF and CF.

After adjustment, the value of Al is still a compressed BCD code, that is, the two compressed BCD codes are added and adjusted, and the result is still a compressed BCD code.

BCD Code Addition Adjustment Command Adjust the result of adding two compressed BCD codes to obtain the correct compressed BCD code result.

out and in are port read and write commands in the assembly. Ports are used by the host and peripherals for data exchange, and are divided into three types: data port, status port and control port.

PCs assign an address to each port, and all ports are arranged linearly to form an IO address space independent of the memory space, which is generally represented in hexadecimal. In 8086, the range of port addresses is 0000h-ffffh.

For example, in al, 21h indicates that a byte of data is read from port 21h to al.

out 21h, al indicates that the data held by al is written to port 21h.

Then the landlord said that 18h and 81h are port numbers, and you need to check which device is the port.

In addition, it should be noted that the address of data input and output should be placed in DX, and the data should be used as the transmission medium, and it is necessary to decide whether to use AL, AH or DL and DH according to the transmission bits. Because the CPU does not support writing the values held by the rest of the registers directly to the port.

In assembly language for the 8086 series.

The In command means to read data from the port, for example, in al, 80h, and read the data from the 80h port into al.

The out command means to output data to the port, e.g. out 80h, al, to output al to the 80h port.

In assembly language, the operation of the CPU peripherals is completed by special port read and write instructions;

Use the in command for read ports and out commands for write ports.

Examples are as follows: in al, 21h; Indicates that one byte of data is read from the 21h port to alin ax, 21h; It indicates that 1 byte of data is read from the port address 21 hours to AL, and 1 byte is read from the port address 22 hours to AH

mov dx,379h

in al,dx ；Read 1 byte from port 379h to alout 21h, al; write the value of al to port 21h out 21h,ax; Write the value of ax to two consecutive bytes starting from 21h of the port address. （port[21h]=al,port[22h]=ah）

mov dx,378h

out dx,ax ；Write AH and AL to ports 379H and 378H, respectively

This directive can be seen this way.

out port address, the data to be output.

Here 18h is the hexadecimal number 18, and 81h represents the port number with the hexadecimal number 81; Out 81h, AL out is to send data from AL to port 81H.