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Re: Serial Port IO

Posted by Guadalupe E Ruiz/MATA1/MFG/KEMET/US on 2000-11-13

To read data or write data to a port, first you have to know the port number (ex. serial port com 1 = 0x3F8 & LPT1 0x378).
and program the baud rate, parity, stop bits only for the serial ports (com 1, 2...), for LPT you can send and read without
programing a value to the port.

Hope this Help!!!

In MsVisual C++ 6, you can use to send data to a port this function:
_outp, _outpw, _outpd

Output a byte(_outp), a word(_outpw), or a double word (_outpd) at a port.

int _outp( unsigned short port, int databyte );
unsigned short _outpw( unsigned short port, unsigned short dataword );
unsigned long _outpd( unsigned short port, unsigned long dataword );

Routine          Required Header   Compatibility
 _outp         <conio.h>  Win 95
_outpw    <conio.h>  Win 95
_outpd         <conio.h>  Win 95

Return Value
 The functions return the data output. There is no error return.

Parameters
     port Port number
     databyte, dataword Output values

Remarks
The _outp, _outpw, and _outpd functions write a byte, a word, and a double word, respectively, to the specified output port.
The port argument can be any unsigned integer in the range 0 ? 65,535; databyte can be any integer in the range 0 ? 255;
and dataword can be any value in the range of an integer, an unsigned short integer, and an unsigned long integer, respectively.


And to read data you can use this one:
_inp, _inpw, _inpd
Input a byte (_inp), a word (_inpw), or a double word (_inpd) from a port.

int _inp( unsigned short port );
unsigned short _inpw( unsigned short port );
unsigned long _inpd( unsigned short port );

Routine         Required Header     Compatibility
_inp       <conio.h>           Win 95
_inpw           <conio.h>           Win 95
_inpd           <conio.h>           Win 95


Return Value
 The functions return the byte, word, or double word read from port. There is no error return.

Parameter
port Port number

Remarks
The _inp, _inpw, and _inpd functions read a byte, a word, and a double word, respectively, from the specified input port.
The input value can be any unsigned short integer in the range 0 ? 65,535.


Feel free to send me an e-mail if you have more questions on I/O using ports.

G. Ruiz
Equipment Enginner

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