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Synchronize timer on repeated events to compensate for lost accuracy.

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Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@2628
This commit is contained in:
Peter Veenstra 2006-05-19 10:34:02 +00:00
parent 2cd6264d32
commit 4775cd6f42
1 changed files with 11 additions and 9 deletions
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20
src/hardware/timer.cpp
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@ -16,7 +16,7 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
/* $Id: timer.cpp,v 1.37 2006-05-18 11:25:46 qbix79 Exp $ */
/* $Id: timer.cpp,v 1.38 2006-05-19 10:34:02 qbix79 Exp $ */
#include <math.h>
#include "dosbox.h"
@ -65,7 +65,10 @@ static bool latched_timerstatus_locked;
static void PIT0_Event(Bitu /*val*/) {
PIC_ActivateIRQ(0);
if (pit[0].mode!=0) PIC_AddEvent(PIT0_Event,pit[0].delay);
if (pit[0].mode != 0) {
pit[0].start = PIC_FullIndex()-pit[0].delay; // resynchronize
PIC_AddEvent(PIT0_Event,pit[0].delay);
}
}
static bool counter_output(Bitu counter) {
@ -146,6 +149,10 @@ static void counter_latch(Bitu counter) {
index*=2;
if (index>p->delay) index-=p->delay;
p->read_latch=(Bit16u)(p->cntr - (index/p->delay)*p->cntr);
// In mode 3 it never returns odd numbers LSB (if odd number is written 1 will be
// subtracted on first clock and then always 2)
// fixes "Corncob 3D"
p->read_latch&=0xfffe;
break;
default:
LOG(LOG_PIT,LOG_ERROR)("Illegal Mode %d for reading counter %d",p->mode,counter);
@ -224,18 +231,13 @@ static Bitu read_latch(Bitu port,Bitu /*iolen*/) {
pit[counter].go_read_latch = true;
break;
case 3: /* read LSB followed by MSB */
// In mode 3 it never returns odd numbers LSB (if odd number is written 1 will be
// subtracted on first clock and then always 2)
// fixes "Corncob 3D"
if((pit[counter].mode&0x7) == 3) ret = (pit[counter].read_latch & 0xfe);
else ret = (pit[counter].read_latch & 0xff);
ret = pit[counter].read_latch & 0xff;
if (pit[counter].mode & 0x80) pit[counter].mode &= 7;
else pit[counter].read_state = 0;
break;
case 1: /* read LSB */
if((pit[counter].mode&0x7) == 3) ret = (pit[counter].read_latch & 0xfe);
else ret = (pit[counter].read_latch & 0xff);
ret = pit[counter].read_latch & 0xff;
pit[counter].go_read_latch = true;
break;
case 2: /* read MSB */