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_stop_count()
{
// stop counting
m_timer->enable(0);
// clear timer output
timer_output(1);
}
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 bitbanger_device::device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr)
{
switch(id)
{
case TIMER_OUTPUT:
timer_output();
break;
case TIMER_INPUT:
timer_input();
break;
}
}
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;
}
}
void i8155_device::device_reset()
{
// clear output registers
m_output[PORT_A] = 0;
m_output[PORT_B] = 0;
m_output[PORT_C] = 0;
// set ports to input mode
register_w(REGISTER_COMMAND, m_command & ~(COMMAND_PA | COMMAND_PB | COMMAND_PC_MASK));
// clear timer flag
m_status &= ~STATUS_TIMER;
// stop counting
m_timer->enable(0);
// clear timer output
m_to = 1;
timer_output();
}
inline void i8155_device::pulse_timer_output()
{
m_to = 0; timer_output();
m_to = 1; timer_output();
}
void i8155_device::register_w(int offset, UINT8 data)
{
switch (offset & 0x07)
{
case REGISTER_COMMAND:
m_command = data;
if (LOG) logerror("8155 '%s' Port A Mode: %s\n", tag(), (data & COMMAND_PA) ? "output" : "input");
if (LOG) logerror("8155 '%s' Port B Mode: %s\n", tag(), (data & COMMAND_PB) ? "output" : "input");
if (LOG) logerror("8155 '%s' Port A Interrupt: %s\n", tag(), (data & COMMAND_IEA) ? "enabled" : "disabled");
if (LOG) logerror("8155 '%s' Port B Interrupt: %s\n", tag(), (data & COMMAND_IEB) ? "enabled" : "disabled");
switch (data & COMMAND_PC_MASK)
{
case COMMAND_PC_ALT_1:
if (LOG) logerror("8155 '%s' Port C Mode: Alt 1\n", tag());
break;
case COMMAND_PC_ALT_2:
if (LOG) logerror("8155 '%s' Port C Mode: Alt 2\n", tag());
break;
case COMMAND_PC_ALT_3:
if (LOG) logerror("8155 '%s' Port C Mode: Alt 3\n", tag());
break;
case COMMAND_PC_ALT_4:
if (LOG) logerror("8155 '%s' Port C Mode: Alt 4\n", tag());
break;
}
switch (data & COMMAND_TM_MASK)
{
case COMMAND_TM_NOP:
// do not affect counter operation
break;
case COMMAND_TM_STOP:
// NOP if timer has not started, stop counting if the timer is running
if (LOG) logerror("8155 '%s' Timer Command: Stop\n", tag());
m_to = 1;
timer_output();
m_timer->enable(0);
break;
case COMMAND_TM_STOP_AFTER_TC:
// stop immediately after present TC is reached (NOP if timer has not started)
if (LOG) logerror("8155 '%s' Timer Command: Stop after TC\n", tag());
break;
case COMMAND_TM_START:
if (LOG) logerror("8155 '%s' Timer Command: Start\n", tag());
if (m_timer->enabled())
{
// if timer is running, start the new mode and CNT length immediately after present TC is reached
}
else
{
// load mode and CNT length and start immediately after loading (if timer is not running)
m_counter = m_count_length & 0x3fff;
m_timer->adjust(attotime::zero, 0, attotime::from_hz(clock()));
}
break;
}
break;
case REGISTER_PORT_A:
write_port(PORT_A, data);
break;
case REGISTER_PORT_B:
write_port(PORT_B, data);
break;
case REGISTER_PORT_C:
write_port(PORT_C, data & 0x3f);
break;
case REGISTER_TIMER_LOW:
m_count_length = (m_count_length & 0xff00) | data;
if (LOG) logerror("8155 '%s' Count Length Low: %04x\n", tag(), m_count_length);
break;
case REGISTER_TIMER_HIGH:
m_count_length = (data << 8) | (m_count_length & 0xff);
if (LOG) logerror("8155 '%s' Count Length High: %04x\n", tag(), m_count_length);
switch (data & TIMER_MODE_MASK)
{
case TIMER_MODE_LOW:
// puts out LOW during second half of count
if (LOG) logerror("8155 '%s' Timer Mode: LOW\n", tag());
break;
case TIMER_MODE_SQUARE_WAVE:
// square wave, i.e. the period of the square wave equals the count length programmed with automatic reload at terminal count
if (LOG) logerror("8155 '%s' Timer Mode: Square wave\n", tag());
break;
case TIMER_MODE_SINGLE_PULSE:
// single pulse upon TC being reached
if (LOG) logerror("8155 '%s' Timer Mode: Single pulse\n", tag());
break;
case TIMER_MODE_AUTOMATIC_RELOAD:
// automatic reload, i.e. single pulse every time TC is reached
if (LOG) logerror("8155 '%s' Timer Mode: Automatic reload\n", tag());
break;
}
break;
}
}