在DELPHI2.0/3.0中直接操作端口

王朝delphi·作者佚名  2006-01-08
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Borland Delphi2.0/3.0以其强大的功能及方便快捷的程序设计

而为广大程序员所喜爱。但是在用它来编写工业控制程序时,需要对

计算机所连接的外部设备进行操作,即直接对I/O地址进行读写操作,

这时该软件就显得有些美中不足了。

针对这一问题,笔者使用Delphi 2.0/3.0以内嵌汇编的方式编写

了一个模块PORT95. PAS,可方便地实现直接对I/O地址的读写操作,代

码简捷且执行速度较快。

使用时只要将PORT95.PAS加到工程文件中,并在users中加上Port

95,就可以在应用程序中直接对I/O端口进行操作。

具体的实现方法及PORT95.PAS的源代码如下:

unit Port95;

interface

function PortReadByte(Addr:Word) : Byte;

function PortReadWord(Addr:Word) : Word;

function PortReadWordLS(Addr:Word) : Word;

procedure PortWriteByte(Addr:Word; Value:Byte);

procedure PortWriteWord(Addr:Word; Value:Word);

procedure PortWriteWordLS(Addr:Word; Value:Word);

implementation

{*

* Port Read byte function

*Parameter:port address

*Return: byte value from given port

*}

function PortReadByte(Addr:Word) : Byte; assembler; regi

ster;

asm

MOV DX,AX

IN AL,DX

end;

{*

* HIGH SPEED Port Read Word function

* Parameter: port address

* Return: word value from given port

* Comment:may problem with some cards and computers that

can't to access whole word, usualy it works.

*}

function PortReadWord(Addr:Word) : Word; assembler; regi

ster;

asm

MOV DX,AX

IN AX,DX

end;

{*

* LOW SPEED Port Read Word function

* Parameter: port address

*Return:word value from given port

*Comment:work in cases,only to adjust DELAY if need

*}

function PortReadWordLS(Addr:Word) : Word; assembler; re

gister;

const

Delay = 150;

// depending of CPU speed and cards speed

asm

MOV DX,AX

IN AL,DX

//read LSB port

MOV ECX,Delay

@1:

LOOP @1 //delay between two reads

XCHG AH,AL

INC DX

//port+1

IN AL,DX //read MSB port

XCHG AH,AL //restore bytes order

end;

{* Port Write byte function*}

procedure PortWriteByte(Addr:Word; Value:Byte); assemble

r; register;

asm

XCHG AX,DX

OUT DX,AL

end;

{*

* HIGH SPEED Port Write word procedure

* Comment:may problem with some cards and computers that

can't to access whole word, usualy it works.

*}

procedure PortWriteWord(Addr:word; Value:word); assemble

r; register;

asm

XCHG AX,DX

OUT DX,AX

end;

{*

* LOW SPEED Port Write Word procedure

*}

procedure PortWriteWordLS(Addr:word; Value:word); assemb

ler; register;

const

Delay = 150;

// depending of CPU speed and cards speed

asm

XCHG AX,DX

OUT DX,AL

MOV ECX,Delay

@1:

LOOP@1

XCHG AH,AL

INC DX

OUT DX,AL

end;

end. //单元结束

上述PORT95.PAS适用于Delphi 2.0/3.0、Windows 95 操作系统

 
 
 
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