/*============= Block IO access : blockio.c =======================

  PURPOSE - show use of block IO and blocking interrupts with an IO
            enabling program.  Usage is-
                ./iopl_start ./block_io

     NOTE - Put a CRO on pin 2 of the PP port to see 1 us data changes.
	    Pins 3-9 act as high order bits of a counter and should
	    also be examined.
*/
#include <stdio.h>
#include <unistd.h>
#include <sys/io.h>         /* for IO access.*/

#define BASEPORT 0x378      /* data port of lp0 ( DOS LPT1) */

int main(int argc, char *argv[])
{/*--- tell user what is happening.*/
   printf("\n   This machine will hangup for about 8 seconds and toggle pins\n") ;
   printf("   2-9 of the first printer port ( lp0).  D0 ( pin 2) outputs\n") ;
   printf("   a 500kHz squarewave,  D1 ( pin 3) 250 kHz down to D7 ( pin 9)\n") ;
   printf("   at about 3.9 kHz.\n\n") ;
     
/*--- fill up a buffer, sent it out with interrupts off.*/
#define ITERATIONS 8000000
   char buffer [ITERATIONS] ;
   int j ;
   for (j=0 ; j<ITERATIONS ; j++)
     buffer[j] = (char)j ;
   asm("cli") ;                          /* disable interrupts. */
   outsb(BASEPORT, buffer, ITERATIONS) ; /* block IO. */
   asm("sti") ;                          /* enable interrupts. */
     
   exit(0); 
}