UINT8 pia6821_device::port_a_r()
{
UINT8 ret = get_in_a_value();
// IRQ flags implicitly cleared by a read
m_irq_a1 = FALSE;
m_irq_a2 = FALSE;
update_interrupts();
// CA2 is configured as output and in read strobe mode
if(C2_OUTPUT(m_ctl_a) && C2_STROBE_MODE(m_ctl_a))
{
// this will cause a transition low
set_out_ca2(FALSE);
// if the CA2 strobe is cleared by the E, reset it right away
if(STROBE_E_RESET(m_ctl_a))
{
set_out_ca2(TRUE);
}
}
LOG(("PIA #%s: port A read = %02X\n", tag(), ret));
return ret;
}
static UINT8 port_a_r(const device_config *device)
{
pia6821_state *p = get_token(device);
UINT8 ret = get_in_a_value(device);
/* IRQ flags implicitly cleared by a read */
p->irq_a1 = FALSE;
p->irq_a2 = FALSE;
update_interrupts(device);
/* CA2 is configured as output and in read strobe mode */
if (C2_OUTPUT(p->ctl_a) && C2_STROBE_MODE(p->ctl_a))
{
/* this will cause a transition low */
set_out_ca2(device, FALSE);
/* if the CA2 strobe is cleared by the E, reset it right away */
if (STROBE_E_RESET(p->ctl_a))
set_out_ca2(device, TRUE);
}
LOG(("PIA #%s: port A read = %02X\n", device->tag, ret));
return ret;
}
static UINT8 get_out_a_value(const device_config *device)
{
pia6821_state *p = get_token(device);
UINT8 ret;
if (p->ddr_a == 0xff)
/* all output */
ret = p->out_a;
else
/* input pins don't change */
ret = (p->out_a & p->ddr_a) | (get_in_a_value(device) & ~p->ddr_a);
return ret;
}
UINT8 pia6821_device::get_out_a_value()
{
UINT8 ret;
if (m_ddr_a == 0xff)
{
// all output
ret = m_out_a;
}
else
{
// input pins don't change
ret = (m_out_a & m_ddr_a) | (get_in_a_value() & ~m_ddr_a);
}
return ret;
}
