Sprinter/mame
2
0
Fork 0
mirror of https://github.com/holub/mame synced 2025-04-23 08:49:55 +03:00
Code Issues Actions 1 Packages Projects Releases Wiki Activity

6840: fix dual byte mode once again (nw) (#4081)

Browse Source 
* 6840: fix dual byte mode once again (nw)

Two problems in dual byte mode:

- the high time flag is the same for all counters
- high time flag is reset on each counter reload, but should
  only be reset if the timer is reload by the user.

* 6840: fix dual byte mode once again (nw)
This commit is contained in:
dxl 2018-10-07 14:51:49 +02:00 committed by R. Belmont
parent b26b436bfb
commit e2665802ec
2 changed files with 18 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
src/devices/machine/6840ptm.cpp
View File

@ -136,7 +136,10 @@ void ptm6840_device::device_reset()
m_status_read_since_int = 0;
m_irq = 0;
m_t3_scaler = 0;
m_hightime = false;
m_hightime[0] = false;
m_hightime[1] = false;
m_hightime[2] = false;
for (int i = 0; i < 3; i++)
{
m_counter[i] = 0xffff;
@ -185,7 +188,7 @@ void ptm6840_device::subtract_from_counter(int counter, int count)
msb--;
// If MSB goes less than zero, we've expired
if ((msb == 0 && !m_hightime) || (msb < 0 && m_hightime))
if ((msb == 0 && !m_hightime[counter]) || (msb < 0 && m_hightime[counter]))
{
timeout(counter);
msb = (m_latch[counter] >> 8) + 1;
@ -224,7 +227,7 @@ void ptm6840_device::subtract_from_counter(int counter, int count)
if (m_control_reg[counter] & COUNT_MODE_8BIT)
{
/* In dual 8 bit mode, let the counter fire when MSB == 0 */
m_hightime = !(clks & 0xff00);
m_hightime[counter] = !(clks & 0xff00);
clks &= 0xff00;
}
@ -349,7 +352,7 @@ void ptm6840_device::reload_count(int idx)
// Copy the latched value in
m_counter[idx] = m_latch[idx];
m_hightime = false;
// If reset is held, don't start counting
if (m_control_reg[0] & RESET_TIMERS)
return;
@ -370,10 +373,11 @@ void ptm6840_device::reload_count(int idx)
int count = m_counter[idx];
if (m_control_reg[idx] & COUNT_MODE_8BIT)
{
if (m_hightime)
if (m_hightime[idx])
count = 0xff;
else
count = ((count >> 8) + 1) * ((count & 0xff) + 1);
}
else
{
@ -521,7 +525,7 @@ WRITE8_MEMBER( ptm6840_device::write )
{
m_timer[i]->enable(false);
m_enabled[i] = 0;
m_hightime = false;
m_hightime[idx] = false;
}
}
// Releasing reset
@ -529,6 +533,7 @@ WRITE8_MEMBER( ptm6840_device::write )
{
for (int i = 0; i < 3; i++)
{
m_hightime[idx] = false;
reload_count(i);
}
}
@ -540,6 +545,7 @@ WRITE8_MEMBER( ptm6840_device::write )
// Changing the clock source? (e.g. Zwackery)
if (diffs & INTERNAL_CLK_EN)
{
m_hightime[idx] = false;
reload_count(idx);
}
break;
@ -568,6 +574,7 @@ WRITE8_MEMBER( ptm6840_device::write )
// Reload the count if in an appropriate mode
if (!(m_control_reg[idx] & 0x10) || (m_control_reg[0] & RESET_TIMERS))
{
m_hightime[idx] = false;
reload_count(idx);
}
@ -597,10 +604,11 @@ void ptm6840_device::timeout(int idx)
{
case 0:
case 2:
if (m_control_reg[idx] & COUNT_MODE_8BIT)
{
m_hightime = !m_hightime;
m_output[idx] = m_hightime;
m_hightime[idx] = !m_hightime[idx];
m_output[idx] = m_hightime[idx];
m_out_cb[idx](m_output[idx]);
}
else
@ -645,6 +653,7 @@ void ptm6840_device::set_gate(int idx, int state)
{
if (state == 0 && m_gate[idx])
{
m_hightime[idx] = false;
reload_count(idx);
}
}

2
src/devices/machine/6840ptm.h
View File

@ -129,7 +129,7 @@ private:
static const char *const opmode[];
// set in dual 8 bit mode to indicate Output high time cycle
bool m_hightime;
bool m_hightime[3];
};