ref: e969575d2e55eec89d3a2765b974e023123d8fa5
dir: /sys/src/cmd/aux/realemu/pit.c/
#include <u.h>
#include <libc.h>
#include "dat.h"
#include "fns.h"
enum {
AC0 = 0,
AC1,
AC2,
Actl,
Readback = 3,
RBC0 = 1<<1,
RBC1 = 1<<2,
RBC2 = 1<<3,
RBlatchstatus = 1<<4,
RBlatchcount = 1<<5,
AMlatchcount = 0,
AMloonly,
AMhionly,
AMlohi,
OM0 = 0,
OM1,
OM2,
OM3,
OM4,
OM5,
OM2b,
OM3b,
};
static void
latchstatus(Pit *ch)
{
if(ch->rlatched)
return;
ch->rlatch[0] = ch->bcd | ch->omode<<1 | ch->amode<<4 | ch->count0<<6 | ch->out<<7;
ch->rcount = 0;
ch->rlatched = 1;
}
static void
latchcount(Pit *ch)
{
ulong w;
if(ch->rlatched)
return;
w = ch->count & 0xFFFF;
if(ch->bcd)
w = (w % 10) | ((w/10) % 10)<<4 | ((w/100) % 10)<<8 | ((w/1000) % 10)<<12;
ch->rlatch[0] = w & 0xFF;
ch->rlatch[1] = (w >> 8) & 0xFF;
ch->rcount = 0;
ch->rlatched = 1;
switch(ch->amode){
case AMhionly:
ch->rcount++;
break;
case AMlohi:
ch->rlatched++;
break;
}
}
static void
setcount(Pit *ch)
{
ulong w;
w = (ulong)ch->wlatch[0] | (ulong)ch->wlatch[1] << 8;
if(ch->bcd)
w = (w & 0xF) + 10*((w >> 4)&0xF) + 100*((w >> 8)&0xF) + 1000*((w >> 12)&0xF);
ch->count = w;
ch->count0 = 0;
}
static int
deccount(Pit *ch, vlong *cycles)
{
if(ch->count0){
*cycles = 0;
return 0;
} else {
vlong passed, remain;
passed = *cycles;
if(ch->count == 0){
ch->count = ch->bcd ? 9999 : 0xFFFF;
passed--;
}
if(passed <= ch->count){
remain = 0;
ch->count -= passed;
} else {
remain = passed - ch->count;
ch->count = 0;
}
*cycles = remain;
return ch->count == 0;
}
}
void
setgate(Pit *ch, uchar gate)
{
if(ch->gate == 0 && gate)
ch->gateraised = 1;
ch->gate = gate;
}
static void
clockpit1(Pit *ch, vlong *cycles)
{
switch(ch->omode){
case OM0: /* Interrupt On Terminal Count */
if(ch->count0){
setcount(ch);
ch->out = 0;
Next:
--*cycles;
return;
}
if(ch->gate && deccount(ch, cycles)){
ch->out = 1;
return;
}
break;
case OM1: /* Hardware Re-triggerable One-shot */
if(ch->gateraised){
ch->gateraised = 0;
setcount(ch);
ch->out = 0;
goto Next;
}
if(deccount(ch, cycles) && ch->out == 0){
ch->out = 1;
return;
}
break;
case OM2: /* Rate Generator */
case OM2b:
ch->out = 1;
if(ch->count0){
setcount(ch);
goto Next;
}
if(ch->gate == 0)
break;
if(ch->gateraised){
ch->gateraised = 0;
setcount(ch);
goto Next;
}
if(deccount(ch, cycles)){
setcount(ch);
ch->out = 0;
return;
}
break;
case OM3: /* Square Wave Generator */
case OM3b:
if(ch->count0){
setcount(ch);
goto Next;
}
if(ch->gate == 0)
break;
if(ch->gateraised){
ch->gateraised = 0;
setcount(ch);
goto Next;
}
if(deccount(ch, cycles)){
setcount(ch);
ch->out ^= 1;
return;
}
break;
case OM4: /* Software Triggered Strobe */
ch->out = 1;
if(ch->count0){
setcount(ch);
goto Next;
}
if(ch->gate && deccount(ch, cycles)){
ch->out = 0;
return;
}
break;
case OM5: /* Hardware Triggered Strobe */
ch->out = 1;
if(ch->gateraised){
ch->gateraised = 0;
setcount(ch);
goto Next;
}
if(deccount(ch, cycles)){
ch->out = 0;
return;
}
break;
}
*cycles = 0;
}
void
clockpit(Pit *pit, vlong cycles)
{
Pit *ch;
int i;
if(cycles <= 0)
return;
for(i = 0; i<Actl; i++){
ch = pit + i;
if(ch->wlatched){
vlong c;
switch(ch->omode){
case OM3:
case OM3b:
c = cycles * 2;
break;
default:
c = cycles;
}
while(c > 0)
clockpit1(ch, &c);
}
ch->gateraised = 0;
}
}
uchar
rpit(Pit *pit, uchar addr)
{
Pit *ch;
uchar data;
if(addr >= Actl)
return 0;
ch = pit + addr;
if(ch->rlatched){
data = ch->rlatch[ch->rcount & 1];
ch->rlatched--;
} else {
data = 0;
switch(ch->amode){
case AMloonly:
data = ch->count & 0xFF;
break;
case AMhionly:
data = (ch->count >> 8) & 0xFF;
break;
case AMlohi:
data = (ch->count >> ((ch->rcount & 1)<<3)) & 0xFF;
break;
}
}
ch->rcount++;
if(0) fprint(2, "rpit %p: %.2x %.2x\n", pit, (int)addr, (int)data);
return data;
}
void
wpit(Pit *pit, uchar addr, uchar data)
{
Pit *ch;
if(0) fprint(2, "wpit %p: %.2x %.2x\n", pit, (int)addr, (int)data);
if(addr > Actl)
return;
if(addr == Actl){
uchar sc, amode, omode, bcd;
bcd = (data & 1);
omode = (data >> 1) & 7;
amode = (data >> 4) & 3;
sc = (data >> 6) & 3;
if(sc == Readback){
ch = nil;
for(;;){
if(data & RBC0){
ch = pit;
break;
}
if(data & RBC1){
ch = pit + 1;
break;
}
if(data & RBC2){
ch = pit + 2;
break;
}
break;
}
if(ch == nil)
return;
if((data & RBlatchcount) == 0)
latchcount(ch);
if((data & RBlatchstatus) == 0)
latchstatus(ch);
return;
}
ch = pit + sc;
if(amode == AMlatchcount){
latchcount(ch);
return;
}
ch->bcd = bcd;
ch->amode = amode;
ch->omode = omode;
ch->rlatched = 0;
ch->rcount = 0;
ch->rlatch[0] = 0;
ch->rlatch[1] = 0;
ch->wlatched = 0;
ch->wcount = 0;
ch->wlatch[0] = 0;
ch->wlatch[1] = 0;
ch->count0 = 1;
ch->out = !!omode;
return;
}
ch = pit + addr;
switch(ch->amode){
case AMloonly:
case AMhionly:
ch->wlatch[ch->amode - AMloonly] = data;
ch->wcount++;
break;
case AMlohi:
ch->wlatch[ch->wcount++ & 1] = data;
if(ch->wcount < 2)
return;
break;
}
ch->wlatched = ch->wcount;
ch->wcount = 0;
ch->count0 = 1;
}