Borland Delphi2.0/3.0以其強大的功能及方便快速的程式設計
而為廣大程式設計師所喜愛。但是在用它來編寫工業控製程式時,需要對
電腦所連接的外部設備進行操作,即直接對I/O位址進行讀寫操作,
這時該軟體就顯得有些美中不足了。
針對此問題,筆者使用Delphi 2.0/3.0以內嵌彙編的方式編寫
了一個模組PORT95. PAS,可方便地實現直接對I/O位址的讀寫操作,代
碼簡捷且執行速度較快。
使用時只要將PORT95.PAS加到工程文件中,並在users中加上Port
95,就可以在應用程式中直接對I/O埠進行操作。
具體的實作方法及PORT95.PAS的源碼如下:
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. //單元結束
上述PORT95.PAS適用於Delphi 2.0/3.0、Windows 95 作業系統
。