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Fix output pins in Dual 8 bit mode (nw)

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In Dual 8 bit mode the output isn't inverted on
every TC, instead it's low until the count reaches 0xff, and
high afterwards.
This commit is contained in:
Sven Schnelle 2018-08-31 21:03:20 +02:00
parent 26e398ac87
commit 889a8606b4
2 changed files with 30 additions and 8 deletions
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31
src/devices/machine/6840ptm.cpp
View File

@ -118,6 +118,7 @@ void ptm6840_device::device_start()
save_item(NAME(m_external_clock)); save_item(NAME(m_external_clock));
save_item(NAME(m_counter)); save_item(NAME(m_counter));
save_item(NAME(m_latch)); save_item(NAME(m_latch));
save_item(NAME(m_hightime));
} }
@ -135,6 +136,7 @@ void ptm6840_device::device_reset()
m_status_read_since_int = 0; m_status_read_since_int = 0;
m_irq = 0; m_irq = 0;
m_t3_scaler = 0; m_t3_scaler = 0;
m_hightime = false;
for (int i = 0; i < 3; i++) for (int i = 0; i < 3; i++)
{ {
m_counter[i] = 0xffff; m_counter[i] = 0xffff;
@ -183,7 +185,7 @@ void ptm6840_device::subtract_from_counter(int counter, int count)
msb--; msb--;
// If MSB goes less than zero, we've expired // If MSB goes less than zero, we've expired
if (msb < 0) if ((msb == 0 && !m_hightime) || (msb < 0 && m_hightime))
{ {
timeout(counter); timeout(counter);
msb = (m_latch[counter] >> 8) + 1; msb = (m_latch[counter] >> 8) + 1;
@ -218,12 +220,19 @@ void ptm6840_device::subtract_from_counter(int counter, int count)
if (m_enabled[counter]) if (m_enabled[counter])
{ {
attotime duration = attotime::from_hz(clk) * m_counter[counter]; int clks = m_counter[counter];
if (m_control_reg[counter] & COUNT_MODE_8BIT)
{
/* In dual 8 bit mode, let the counter fire when MSB == 0 */
m_hightime = !(clks & 0xff00);
clks &= 0xff00;
}
attotime duration = attotime::from_hz(clk) * clks;
if (counter == 2) if (counter == 2)
{ {
duration *= m_t3_divisor; duration *= m_t3_divisor;
} }
m_timer[counter]->adjust(duration); m_timer[counter]->adjust(duration);
} }
} }
@ -340,7 +349,7 @@ void ptm6840_device::reload_count(int idx)
// Copy the latched value in // Copy the latched value in
m_counter[idx] = m_latch[idx]; m_counter[idx] = m_latch[idx];
m_hightime = false;
// If reset is held, don't start counting // If reset is held, don't start counting
if (m_control_reg[0] & RESET_TIMERS) if (m_control_reg[0] & RESET_TIMERS)
return; return;
@ -361,6 +370,9 @@ void ptm6840_device::reload_count(int idx)
int count = m_counter[idx]; int count = m_counter[idx];
if (m_control_reg[idx] & COUNT_MODE_8BIT) if (m_control_reg[idx] & COUNT_MODE_8BIT)
{ {
if (m_hightime)
count = 0xff;
else
count = ((count >> 8) + 1) * ((count & 0xff) + 1); count = ((count >> 8) + 1) * ((count & 0xff) + 1);
} }
else else
@ -509,6 +521,7 @@ WRITE8_MEMBER( ptm6840_device::write )
{ {
m_timer[i]->enable(false); m_timer[i]->enable(false);
m_enabled[i] = 0; m_enabled[i] = 0;
m_hightime = false;
} }
} }
// Releasing reset // Releasing reset
@ -584,9 +597,15 @@ void ptm6840_device::timeout(int idx)
{ {
case 0: case 0:
case 2: case 2:
m_output[idx] = m_output[idx] ^ 1; if (m_control_reg[idx] & COUNT_MODE_8BIT) {
LOG("**ptm6840 t%d output %d **\n", idx + 1, m_output[idx]); m_hightime ^= true;
m_output[idx] = m_hightime;
m_out_cb[idx](m_output[idx]); m_out_cb[idx](m_output[idx]);
} else {
m_output[idx] = m_output[idx] ^ 1;
m_out_cb[idx](m_output[idx]);
}
LOG("%6.6f: **ptm6840 t%d output %d **\n", machine().time().as_double(), idx + 1, m_output[idx]);
break; break;
case 4: case 4:

3
src/devices/machine/6840ptm.h
View File

@ -127,6 +127,9 @@ private:
uint16_t m_counter[3]; uint16_t m_counter[3];
static const char *const opmode[]; static const char *const opmode[];
// set in dual 8 bit mode to indicate Output high time cycle
bool m_hightime;
}; };