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-adc0808: Reduced CPU overhead by smarter timer usage. [Ryan Holtz]

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This commit is contained in:
mooglyguy 2018-04-30 12:14:27 +02:00
parent 507399697b
commit 1e82f36a94
2 changed files with 24 additions and 33 deletions
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54
src/devices/machine/adc0808.cpp
View File

@ -45,7 +45,7 @@ adc0808_device::adc0808_device(const machine_config &mconfig, device_type type,
m_in_cb{ {*this}, {*this}, {*this}, {*this}, {*this}, {*this}, {*this}, {*this} },
m_state(STATE_IDLE),
m_cycle_timer(nullptr),
m_start(0), m_cycle(0), m_step(0), m_address(0), m_sar(0xff), m_eoc(true), m_eoc_pending(false)
m_start(0), m_address(0), m_sar(0xff), m_eoc(1)
{
}
@ -92,12 +92,9 @@ void adc0808_device::device_start()
// register for save states
save_item(NAME(m_state));
save_item(NAME(m_start));
save_item(NAME(m_cycle));
save_item(NAME(m_step));
save_item(NAME(m_address));
save_item(NAME(m_sar));
save_item(NAME(m_eoc));
save_item(NAME(m_eoc_pending));
}
//-------------------------------------------------
@ -106,37 +103,34 @@ void adc0808_device::device_start()
void adc0808_device::device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr)
{
// eoc is delayed one cycle
if (m_eoc_pending)
switch (m_state)
{
m_eoc = true;
m_eoc_cb(1);
m_eoc_ff_cb(1);
m_eoc_pending = false;
}
case STATE_IDLE:
m_cycle_timer->adjust(attotime::never);
m_eoc = 1;
m_eoc_cb(m_eoc);
m_eoc_ff_cb(1);
return;
// start of conversion cycle
if (m_cycle == 0 && m_state == STATE_CONVERSION_START)
m_state = STATE_CONVERSION_RUNNING;
// start of conversion cycle
case STATE_CONVERSION_START:
m_state = STATE_CONVERSION_RUNNING;
// the conversion takes 8 steps every 8 cycles
m_cycle_timer->adjust(attotime::from_hz(clock()) * 63);
return;
// end of conversion cycle
if (m_cycle == 7 && m_state == STATE_CONVERSION_RUNNING)
{
// the conversion takes 8 steps every 8 cycles
if (m_step++ == 7)
{
m_step = 0;
// end of conversion cycle
case STATE_CONVERSION_RUNNING:
m_sar = m_in_cb[m_address](0);
m_eoc_pending = true;
m_state = STATE_IDLE;
if (VERBOSE)
logerror("Conversion finished, result %02x\n", m_sar);
}
}
// next cycle
m_cycle = (m_cycle + 1) & 7;
// eoc is delayed by one cycle
m_cycle_timer->adjust(attotime::from_hz(clock()));
break;
}
}
@ -168,13 +162,13 @@ WRITE_LINE_MEMBER( adc0808_device::start_w )
if (m_start == 1 && state == 0)
{
m_state = STATE_CONVERSION_START;
m_cycle_timer->adjust(attotime::zero);
}
else if (m_start == 0 && state == 1)
{
m_sar = 0;
m_eoc = false;
m_eoc_cb(0);
m_eoc_pending = false;
m_eoc = 0;
m_eoc_cb(m_eoc);
}
m_start = state;
@ -182,7 +176,7 @@ WRITE_LINE_MEMBER( adc0808_device::start_w )
READ_LINE_MEMBER( adc0808_device::eoc_r )
{
return m_eoc ? 1 : 0;
return m_eoc;
}
WRITE8_MEMBER( adc0808_device::address_offset_start_w )

3
src/devices/machine/adc0808.h
View File

@ -127,12 +127,9 @@ private:
// state
int m_start;
int m_cycle;
int m_step;
int m_address;
uint8_t m_sar;
bool m_eoc;
bool m_eoc_pending;
};
class adc0809_device : public adc0808_device