static void timer_2_timeout(int dummy)
{
if (m6840_cr[1] & 0x40)
{
/* set interrupt flags */
m6840_status |= 0x82;
cchasm_6840_irq(ASSERT_LINE);
}
}
void cchasm_6840_w(int offset, int data)
{
/* From datasheet:
0 0 - write control reg 1/3 (reg 1 if lsb of Reg 2 is 1, else 3)
2 1 - write control reg 2
4 2 - write msb buffer reg
6 3 - write timer 1 latch
8 4 - msb buffer register
a 5 - write timer 2 latch
c 6 - msb buffer reg
e 7 - write timer 3 latch
So:
Write ff0100 to 6840 02 = }
Write ff0000 to 6840 00 = } Write 0 to control reg 1
Write ff0000 to 6840 02
Write ff0000 to 6840 0c
Write ff3500 to 6840 0e = } Write 0035 to timer 3 latch?
Write ff0a00 to 6840 00 = } Write 0a to control reg 3
*/
data &= 0xff;
switch (offset) {
case 0x0: /* CR1/3 */
m6840_cr[m6840_cr_select] = data;
if (m6840_cr_select==0)
{
if ((data&0x1))
{
int i;
if (errorlog) fprintf(errorlog,"MC6840: Internal reset\n");
for (i=0; i<3; i++) {
m6840_timerLSB[i]=255;
m6840_timerMSB[i]=255;
}
}
else
if (errorlog) fprintf(errorlog,"MC6840: Timers go!\n");
}
else if (m6840_cr_select==2) {
if (data&0x1) {
if (errorlog) fprintf(errorlog,"MC6840: Divide by 8 prescaler selected\n");
}
}
/* Following bits apply to both registers */
if (data&0x2) {
if (errorlog) fprintf(errorlog,"MC6840: Internal clock selected on CR %d\n",m6840_cr_select);
else
if (errorlog) fprintf(errorlog,"MC6840: External clock selected on CR %d\n",m6840_cr_select);
}
if (data&0x4) {
if (errorlog) fprintf(errorlog,"MC6840: Dual 8 bit count mode selected on CR %d\n",m6840_cr_select);
else
if (errorlog) fprintf(errorlog,"MC6840: 16 bit count mode selected on CR %d\n",m6840_cr_select);
}
if (errorlog) fprintf(errorlog," Write %02x to control register 1/3\n",data);
break;
case 0x2:
m6840_cr[1] = data;
if (data&0x1)
{
m6840_cr_select=0;
if (errorlog) fprintf(errorlog,"MC6840: Control register 1 selected\n");
}
else {
m6840_cr_select=2;
if (errorlog) fprintf(errorlog,"MC6840: Control register 3 selected\n");
}
if (data&0x80)
if (errorlog) fprintf(errorlog,"MC6840: Cr2 Timer output enabled\n");
if (data&0x40)
if (errorlog) fprintf(errorlog,"MC6840: Cr2 interrupt output enabled\n");
if (errorlog) fprintf(errorlog," Write %02x to control register 2\n",data);
break;
case 0x4:
m6840_timerMSB[0]=data;
m6840_status &= ~0x01;
if (errorlog) fprintf(errorlog," Write %02x to MSB of Timer 1\n",data);
break;
case 0x6:
m6840_status &= ~0x01;
m6840_timerLSB[0]=data;
if (errorlog) fprintf(errorlog," Write %02x to LSB of Timer 1\n",data);
break;
case 0x8:
m6840_status &= ~0x02;
cchasm_6840_irq(CLEAR_LINE);
m6840_timerMSB[1]=data;
if ((m6840_cr[1] & 0x38) == 0)
timer_set (TIME_IN_NSEC(M6840_CYCLE) * ((m6840_timerMSB[1]<<8) | m6840_timerLSB[1]), 0, timer_2_timeout);
if (errorlog) fprintf(errorlog," Write %02x to MSB of Timer 2\n",data);
break;
case 0xa:
m6840_status &= ~0x02;
cchasm_6840_irq(CLEAR_LINE);
m6840_timerLSB[1]=data;
if (errorlog) fprintf(errorlog," Write %02x to LSB of Timer 2\n",data);
break;
case 0xc:
m6840_status &= ~0x04;
m6840_timerMSB[2]=data;
if (errorlog) fprintf(errorlog," Write %02x to MSB of Timer 3\n",data);
break;
case 0xe:
m6840_status &= ~0x04;
m6840_timerLSB[2]=data;
if (errorlog) fprintf(errorlog," Write %02x to LSB of Timer 3\n",data);
break;
}
/* if (errorlog) fprintf(errorlog,"Write %04x to 6840 %02x\n",data,offset); */
}
