Outputs a byte (_outp) or a word (_outpw) at a port.
| #include <conio.h> | Required only for function declarations |
int _outp( unsigned port, int databyte );
unsigned _outpw( unsigned port, unsigned dataword );
| port | Port number | |
| databyte | Output value | |
| dataword | Output value |
The _outp and _outpw functions write a byte and a word, respectively, to the specified output port. The port argument can be any unsigned integer in the range 0 – 65,535; byte can be any integer in the range 0 – 255; and dataword can be any value in the range 0 – 65,535.
The functions return the data output. There is no error return.
Standards:None
16-Bit:DOS
32-Bit:None
/* OUTP.C: This program uses _inp and _outp to make sound of variable tone
* and duration.
*/
#include <conio.h>
#include <stdio.h>
#include <time.h>
void Beep( unsigned duration, unsigned frequency ); /* Prototypes */
void Sleep( clock_t _wait );
void main ( main )
{
Beep( 698, 700 );
Beep( 523, 500 );
}
/* Sounds the speaker for a time specified in microseconds by duration
* at a pitch specified in hertz by frequency.
*/
void Beep( unsigned frequency, unsigned duration )
{
int control;
/* If frequency is 0, Beep doesn't try to make a sound. */
if( frequency )
{
/* 75 is about the shortest reliable duration of a sound. */
if( duration < 75 )
duration = 75;
/* Prepare timer by sending 10111100 to port 43. */
_outp( 0x43, 0xb6 );
/* Divide input frequency by timer ticks per second and
* write (byte by byte) to timer.
*/
frequency = (unsigned)(1193180L / frequency);
_outp( 0x42, (char)frequency );
_outp( 0x42, (char)(frequency >> 8) );
/* Save speaker control byte. */
control = _inp( 0x61 );
/* Turn on the speaker (with bits 0 and 1). */
_outp( 0x61, control | 0x3 );
}
Sleep( (clock_t)duration );
/* Turn speaker back on if necessary. */
if( frequency )
_outp( 0x61, control );
}
/* Pauses for a specified number of microseconds. */
void Sleep( clock_t _wait )
{
clock_t goal;
goal = _wait + clock();
while( goal > clock() )
;
}