void i8155_device::device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr)
{
// count down
m_counter--;
if (get_timer_mode() == TIMER_MODE_LOW)
{
// pulse on every count
pulse_timer_output();
}
if (m_counter == 0)
{
if (LOG) logerror("8155 '%s' Timer Count Reached\n", tag());
switch (m_command & COMMAND_TM_MASK)
{
case COMMAND_TM_STOP_AFTER_TC:
// stop timer
m_timer->enable(0);
if (LOG) logerror("8155 '%s' Timer Stopped\n", tag());
break;
}
switch (get_timer_mode())
{
case TIMER_MODE_SQUARE_WAVE:
// toggle timer output
m_to = !m_to;
timer_output();
break;
case TIMER_MODE_SINGLE_PULSE:
// single pulse upon TC being reached
pulse_timer_output();
// clear timer mode setting
m_command &= ~COMMAND_TM_MASK;
break;
case TIMER_MODE_AUTOMATIC_RELOAD:
// automatic reload, i.e. single pulse every time TC is reached
pulse_timer_output();
break;
}
// set timer flag
m_status |= STATUS_TIMER;
// reload timer counter
m_counter = m_count_length & 0x3fff;
}
}
void i8155_device::device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr)
{
if (m_count_extra)
{
m_count_extra = false;
return;
}
// count down by twos
m_counter -= 2;
if (m_counter == 1)
{
LOGMASKED(LOG_TIMER, "Timer count half finished\n");
// reload the even half of the count
m_counter = m_count_loaded & 0x3ffe;
// square wave modes produce a low output in the second half of the counting period
if ((get_timer_mode() & TIMER_MODE_TC_PULSE) == 0)
timer_output(0);
}
else if (m_counter == 2)
{
if ((get_timer_mode() & TIMER_MODE_TC_PULSE) != 0)
{
// pulse low on TC being reached
timer_output(0);
}
// set timer flag
m_status |= STATUS_TIMER;
}
else if (m_counter == 0)
{
timer_output(1);
if ((get_timer_mode() & TIMER_MODE_AUTO_RELOAD) == 0 || (m_command & COMMAND_TM_MASK) == COMMAND_TM_STOP_AFTER_TC)
{
// stop timer
timer_stop_count();
LOGMASKED(LOG_TIMER, "Timer stopped\n");
}
else
{
// automatically reload the counter
timer_reload_count();
}
}
}
inline void i8155_device::timer_reload_count()
{
m_count_loaded = m_count_length;
// valid counts range from 2 to 3FFF
if ((m_count_length & 0x3fff) < 2)
{
timer_stop_count();
return;
}
// begin the odd half of the count, with one extra cycle if count is odd
m_counter = (m_count_loaded & 0x3ffe) | 1;
m_count_extra = BIT(m_count_loaded, 0);
// set up our timer
m_timer->adjust(attotime::zero, 0, clocks_to_attotime(1));
timer_output(1);
switch (get_timer_mode())
{
case 0:
// puts out LOW during second half of count
LOGMASKED(LOG_TIMER, "Timer loaded with %d (Mode: LOW)\n", m_count_loaded & 0x3fff);
break;
case TIMER_MODE_AUTO_RELOAD:
// square wave, i.e. the period of the square wave equals the count length programmed with automatic reload at terminal count
LOGMASKED(LOG_TIMER, "Timer loaded with %d (Mode: Square wave)\n", m_count_loaded & 0x3fff);
break;
case TIMER_MODE_TC_PULSE:
// single pulse upon TC being reached
LOGMASKED(LOG_TIMER, "Timer loaded with %d (Mode: Single pulse)\n", m_count_loaded & 0x3fff);
break;
case TIMER_MODE_TC_PULSE | TIMER_MODE_AUTO_RELOAD:
// automatic reload, i.e. single pulse every time TC is reached
LOGMASKED(LOG_TIMER, "Timer loaded with %d (Mode: Automatic reload)\n", m_count_loaded & 0x3fff);
break;
}
}
