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 。
