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;
}
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;
}
void C6821::SetCA1(BYTE byData)
{
byData = byData ? 1 : 0;
// the new state has caused a transition
if ( m_byCA1 ^ byData )
{
// handle the active transition
if ( ( byData && C1_LOW_TO_HIGH( m_byCTLA ) ) ||
( !byData && C1_HIGH_TO_LOW( m_byCTLA ) ) )
{
// mark the IRQ
SET_IRQ1(m_byCTLA);
// update externals
UpdateInterrupts();
// CA2 is configured as output and in read strobe mode and cleared by a CA1 transition
if ( C2_OUTPUT( m_byCTLA ) && C2_STROBE_MODE( m_byCTLA ) && STROBE_C1_RESET( m_byCTLA ) )
{
// call the CA2 output function
if ( !m_byOCA2 )
PIA_W_CALLBACK( m_stOutCA2, 1 );
// clear CA2
m_byOCA2 = 1;
}
}
}
// set the new value for CA1
m_byCA1 = byData;
}
void pia6821_device::port_b_w(UINT8 data)
{
// buffer the output value
m_out_b = data;
send_to_out_b_func("port B write");
// CB2 in write strobe mode
if(C2_STROBE_MODE(m_ctl_b))
{
// this will cause a transition low
set_out_cb2(FALSE);
// if the CB2 strobe is cleared by the E, reset it right away
if(STROBE_E_RESET(m_ctl_b))
{
set_out_cb2(TRUE);
}
}
}
static void port_b_w(const device_config *device, UINT8 data)
{
pia6821_state *p = get_token(device);
/* buffer the output value */
p->out_b = data;
send_to_out_b_func(device, "port B write");
/* CB2 in write strobe mode */
if (C2_STROBE_MODE(p->ctl_b))
{
/* this will cause a transition low */
set_out_cb2(device, FALSE);
/* if the CB2 strobe is cleared by the E, reset it right away */
if (STROBE_E_RESET(p->ctl_b))
set_out_cb2(device, TRUE);
}
}
void pia_set_input_cb1 (int which, int data)
{
struct pia6821 *p = pia + which;
/* limit the data to 0 or 1 */
data = data ? 1 : 0;
/* the new state has caused a transition */
if (p->in_cb1 ^ data)
{
/* handle the active transition */
if ((data && C1_LOW_TO_HIGH (p->ctl_b)) || (!data && C1_HIGH_TO_LOW (p->ctl_b)))
{
/* mark the IRQ */
p->irq_b1 = 1;
/* call the IRQ function if enabled */
if (IRQ1_ENABLED (p->ctl_b))
if (p->irq_b_func) p->irq_b_func ();
/* CB2 is configured as output and in write strobe mode and cleared by a CA1 transition */
if (C2_OUTPUT (p->ctl_b) && C2_STROBE_MODE (p->ctl_b) && STROBE_C1_RESET (p->ctl_b))
{
/* the IRQ1 flag must have also been cleared */
if (!p->irq_b1)
{
/* call the CB2 output function */
if (!p->out_cb2)
if (p->out_cb2_func) p->out_cb2_func (0, 1);
/* clear CB2 */
p->out_cb2 = 1;
}
}
}
}
/* set the new value for CB1 */
p->in_cb1 = data;
}
UINT8 pia6821_device::port_b_r()
{
UINT8 ret = get_in_b_value();
// This read will implicitly clear the IRQ B1 flag. If CB2 is in write-strobe
// mode with CB1 restore, and a CB1 active transition set the flag,
// clearing it will cause CB2 to go high again. Note that this is different
// from what happens with port A.
if(m_irq_b1 && C2_STROBE_MODE(m_ctl_b) && STROBE_C1_RESET(m_ctl_b))
{
set_out_cb2(TRUE);
}
// IRQ flags implicitly cleared by a read
m_irq_b1 = FALSE;
m_irq_b2 = FALSE;
update_interrupts();
LOG(("PIA #%s: port B read = %02X\n", tag(), ret));
return ret;
}
static UINT8 port_b_r(const device_config *device)
{
pia6821_state *p = get_token(device);
UINT8 ret = get_in_b_value(device);
/* This read will implicitly clear the IRQ B1 flag. If CB2 is in write-strobe
mode with CB1 restore, and a CB1 active transition set the flag,
clearing it will cause CB2 to go high again. Note that this is different
from what happens with port A. */
if (p->irq_b1 && C2_STROBE_MODE(p->ctl_b) && STROBE_C1_RESET(p->ctl_b))
set_out_cb2(device, TRUE);
/* IRQ flags implicitly cleared by a read */
p->irq_b1 = FALSE;
p->irq_b2 = FALSE;
update_interrupts(device);
LOG(("PIA #%s: port B read = %02X\n", device->tag, ret));
return ret;
}
void pia_set_input_ca1(int which, int data)
{
struct pia6821 *p = pia + which;
/* limit the data to 0 or 1 */
data = data ? 1 : 0;
/* the new state has caused a transition */
if (p->in_ca1 ^ data)
{
/* handle the active transition */
if ((data && C1_LOW_TO_HIGH(p->ctl_a)) || (!data && C1_HIGH_TO_LOW(p->ctl_a)))
{
/* mark the IRQ */
p->irq_a1 = 1;
/* update externals */
update_6821_interrupts(p);
/* CA2 is configured as output and in read strobe mode and cleared by a CA1 transition */
if (C2_OUTPUT(p->ctl_a) && C2_STROBE_MODE(p->ctl_a) && STROBE_C1_RESET(p->ctl_a))
{
/* call the CA2 output function */
if (!p->out_ca2)
if (p->intf->out_ca2_func) p->intf->out_ca2_func(0, 1);
/* clear CA2 */
p->out_ca2 = 1;
}
}
}
/* set the new value for CA1 */
p->in_ca1 = data;
p->in_set |= PIA_IN_SET_CA1;
}
void pia_write (int which, int offset, int data)
{
struct pia6821 *p = pia + which;
switch (pia_offsets[offset & 7])
{
/******************* port A output/DDR write *******************/
case 0:
/* write output register */
if (OUTPUT_SELECTED (p->ctl_a))
{
/* update the output value */
p->out_a = data & p->ddr_a;
/* send it to the output function */
if (p->out_a_func) p->out_a_func (0, p->out_a);
}
/* write DDR register */
else
p->ddr_a = data;
break;
/******************* port B output/DDR write *******************/
case 1:
/* write output register */
if (OUTPUT_SELECTED (p->ctl_b))
{
/* update the output value */
p->out_b = data & p->ddr_b;
/* send it to the output function */
if (p->out_b_func) p->out_b_func (0, p->out_b);
/* CB2 is configured as output and in write strobe mode */
if (C2_OUTPUT (p->ctl_b) && C2_STROBE_MODE (p->ctl_b))
{
/* this will cause a transition low; call the output function if we're currently high */
if (p->out_cb2)
if (p->out_cb2_func) p->out_cb2_func (0, 0);
p->out_cb2 = 0;
/* if the CB2 strobe is cleared by the E, reset it right away */
if (STROBE_E_RESET (p->ctl_b))
{
if (p->out_cb2_func) p->out_cb2_func (0, 1);
p->out_cb2 = 1;
}
}
}
/* write DDR register */
else
p->ddr_b = data;
break;
/******************* port A control write *******************/
case 2:
/* CA2 is configured as output and in set/reset mode */
/* 10/22/98 - MAB/FMP - any C2_OUTPUT should affect CA2 */
if (C2_OUTPUT (data))
{
/* determine the new value */
int temp = SET_C2 (data) ? 1 : 0;
/* if this creates a transition, call the CA2 output function */
if (p->out_ca2 ^ temp)
if (p->out_ca2_func) p->out_ca2_func (0, temp);
/* set the new value */
p->out_ca2 = temp;
}
/* update the control register */
p->ctl_a = data;
break;
/******************* port B control write *******************/
case 3:
/* CB2 is configured as output and in set/reset mode */
/* 10/22/98 - MAB/FMP - any C2_OUTPUT should affect CB2 */
if (C2_OUTPUT (data))
{
/* determine the new value */
int temp = SET_C2 (data) ? 1 : 0;
/* if this creates a transition, call the CA2 output function */
if (p->out_cb2 ^ temp)
if (p->out_cb2_func) p->out_cb2_func (0, temp);
/* set the new value */
p->out_cb2 = temp;
}
/* update the control register */
p->ctl_b = data;
break;
}
}
int pia_read (int which, int offset)
{
struct pia6821 *p = pia + which;
int val = 0;
switch (pia_offsets[offset & 7])
{
/******************* port A output/DDR read *******************/
case 0:
/* read output register */
if (OUTPUT_SELECTED (p->ctl_a))
{
/* update the input */
if (p->in_a_func) p->in_a = p->in_a_func (0);
/* combine input and output values */
val = (p->out_a & p->ddr_a) + (p->in_a & ~p->ddr_a);
/* IRQ flags implicitly cleared by a read */
p->irq_a1 = p->irq_a2 = 0;
/* 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; call the output function if we're currently high */
if (p->out_ca2)
if (p->out_ca2_func) p->out_ca2_func (0, 0);
p->out_ca2 = 0;
/* if the CA2 strobe is cleared by the E, reset it right away */
if (STROBE_E_RESET (p->ctl_a))
{
if (p->out_ca2_func) p->out_ca2_func (0, 1);
p->out_ca2 = 1;
}
}
}
/* read DDR register */
else
val = p->ddr_a;
break;
/******************* port B output/DDR read *******************/
case 1:
/* read output register */
if (OUTPUT_SELECTED (p->ctl_b))
{
/* update the input */
if (p->in_b_func) p->in_b = p->in_b_func (0);
/* combine input and output values */
val = (p->out_b & p->ddr_b) + (p->in_b & ~p->ddr_b);
/* IRQ flags implicitly cleared by a read */
p->irq_b1 = p->irq_b2 = 0;
}
/* read DDR register */
else
val = p->ddr_b;
break;
/******************* port A control read *******************/
case 2:
/* Update CA1 & CA2 if callback exists, these in turn may update IRQ's */
if (p->in_ca1_func) pia_set_input_ca1(which, p->in_ca1_func (0));
if (p->in_ca2_func) pia_set_input_ca2(which, p->in_ca2_func (0));
/* read control register */
val = p->ctl_a;
/* set the IRQ flags if we have pending IRQs */
if (p->irq_a1) val |= PIA_IRQ1;
if (p->irq_a2 && C2_INPUT (p->ctl_a)) val |= PIA_IRQ2;
break;
/******************* port B control read *******************/
case 3:
/* Update CB1 & CB2 if callback exists, these in turn may update IRQ's */
if (p->in_cb1_func) pia_set_input_cb1(which, p->in_cb1_func (0));
if (p->in_cb2_func) pia_set_input_cb2(which, p->in_cb2_func (0));
/* read control register */
val = p->ctl_b;
/* set the IRQ flags if we have pending IRQs */
if (p->irq_b1) val |= PIA_IRQ1;
if (p->irq_b2 && C2_INPUT (p->ctl_b)) val |= PIA_IRQ2;
break;
}
return val;
}
void pia_write(int which, int offset, int data)
{
struct pia6821 *p = pia + which;
/* adjust offset for 16-bit and ordering */
offset &= 3;
if (p->addr & PIA_ALTERNATE_ORDERING) offset = swizzle_address[offset];
switch (offset)
{
/******************* port A output/DDR write *******************/
case PIA_DDRA:
/* write output register */
if (OUTPUT_SELECTED(p->ctl_a))
{
LOG(("%04x: PIA%d port A write = %02X\n", activecpu_get_previouspc(), which, data));
/* update the output value */
p->out_a = data;/* & p->ddr_a; */ /* NS990130 - don't mask now, DDR could change later */
/* send it to the output function */
if (p->intf->out_a_func && p->ddr_a) p->intf->out_a_func(0, p->out_a & p->ddr_a); /* NS990130 */
}
/* write DDR register */
else
{
LOG(("%04x: PIA%d DDR A write = %02X\n", activecpu_get_previouspc(), which, data));
if (p->ddr_a != data)
{
/* NS990130 - if DDR changed, call the callback again */
p->ddr_a = data;
/* send it to the output function */
if (p->intf->out_a_func && p->ddr_a) p->intf->out_a_func(0, p->out_a & p->ddr_a);
}
}
break;
/******************* port B output/DDR write *******************/
case PIA_DDRB:
/* write output register */
if (OUTPUT_SELECTED(p->ctl_b))
{
LOG(("%04x: PIA%d port B write = %02X\n", activecpu_get_previouspc(), which, data));
/* update the output value */
p->out_b = data;/* & p->ddr_b */ /* NS990130 - don't mask now, DDR could change later */
/* send it to the output function */
if (p->intf->out_b_func && p->ddr_b) p->intf->out_b_func(0, p->out_b & p->ddr_b); /* NS990130 */
/* CB2 is configured as output and in write strobe mode */
if (C2_OUTPUT(p->ctl_b) && C2_STROBE_MODE(p->ctl_b))
{
/* this will cause a transition low; call the output function if we're currently high */
if (p->out_cb2)
if (p->intf->out_cb2_func) p->intf->out_cb2_func(0, 0);
p->out_cb2 = 0;
/* if the CB2 strobe is cleared by the E, reset it right away */
if (STROBE_E_RESET(p->ctl_b))
{
if (p->intf->out_cb2_func) p->intf->out_cb2_func(0, 1);
p->out_cb2 = 1;
}
}
}
/* write DDR register */
else
{
LOG(("%04x: PIA%d DDR B write = %02X\n", activecpu_get_previouspc(), which, data));
if (p->ddr_b != data)
{
/* NS990130 - if DDR changed, call the callback again */
p->ddr_b = data;
/* send it to the output function */
if (p->intf->out_b_func && p->ddr_b) p->intf->out_b_func(0, p->out_b & p->ddr_b);
}
}
break;
/******************* port A control write *******************/
case PIA_CTLA:
/* Bit 7 and 6 read only - PD 16/01/00 */
data &= 0x3f;
LOG(("%04x: PIA%d control A write = %02X\n", activecpu_get_previouspc(), which, data));
/* CA2 is configured as output and in set/reset mode */
/* 10/22/98 - MAB/FMP - any C2_OUTPUT should affect CA2 */
// if (C2_OUTPUT(data) && C2_SET_MODE(data))
if (C2_OUTPUT(data))
{
/* determine the new value */
int temp = SET_C2(data) ? 1 : 0;
/* if this creates a transition, call the CA2 output function */
if (p->out_ca2 ^ temp)
if (p->intf->out_ca2_func) p->intf->out_ca2_func(0, temp);
/* set the new value */
p->out_ca2 = temp;
}
/* update the control register */
p->ctl_a = data;
/* update externals */
update_6821_interrupts(p);
break;
/******************* port B control write *******************/
case PIA_CTLB:
/* Bit 7 and 6 read only - PD 16/01/00 */
data &= 0x3f;
LOG(("%04x: PIA%d control B write = %02X\n", activecpu_get_previouspc(), which, data));
/* CB2 is configured as output and in set/reset mode */
/* 10/22/98 - MAB/FMP - any C2_OUTPUT should affect CB2 */
// if (C2_OUTPUT(data) && C2_SET_MODE(data))
if (C2_OUTPUT(data))
{
/* determine the new value */
int temp = SET_C2(data) ? 1 : 0;
/* if this creates a transition, call the CA2 output function */
if (p->out_cb2 ^ temp)
if (p->intf->out_cb2_func) p->intf->out_cb2_func(0, temp);
/* set the new value */
p->out_cb2 = temp;
}
/* update the control register */
p->ctl_b = data;
/* update externals */
update_6821_interrupts(p);
break;
}
}
int pia_read(int which, int offset)
{
struct pia6821 *p = pia + which;
int val = 0;
/* adjust offset for 16-bit and ordering */
offset &= 3;
if (p->addr & PIA_ALTERNATE_ORDERING) offset = swizzle_address[offset];
switch (offset)
{
/******************* port A output/DDR read *******************/
case PIA_DDRA:
/* read output register */
if (OUTPUT_SELECTED(p->ctl_a))
{
/* update the input */
if ((FPTR)(p->intf->in_a_func) > 0x100)
p->in_a = p->intf->in_a_func(0);
#ifdef MAME_DEBUG
else if ((p->ddr_a ^ 0xff) && !(p->in_set & PIA_IN_SET_A)) {
logerror("PIA%d: Warning! no port A read handler. Assuming pins %02x not connected\n",
which, p->ddr_a ^ 0xff);
p->in_set |= PIA_IN_SET_A; // disable logging
}
#endif // MAME_DEBUG
/* combine input and output values */
val = (p->out_a & p->ddr_a) + (p->in_a & ~p->ddr_a);
/* IRQ flags implicitly cleared by a read */
p->irq_a1 = p->irq_a2 = 0;
update_6821_interrupts(p);
/* 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; call the output function if we're currently high */
if (p->out_ca2)
if (p->intf->out_ca2_func) p->intf->out_ca2_func(0, 0);
p->out_ca2 = 0;
/* if the CA2 strobe is cleared by the E, reset it right away */
if (STROBE_E_RESET(p->ctl_a))
{
if (p->intf->out_ca2_func) p->intf->out_ca2_func(0, 1);
p->out_ca2 = 1;
}
}
LOG(("%04x: PIA%d read port A = %02X\n", activecpu_get_previouspc(), which, val));
}
/* read DDR register */
else
{
val = p->ddr_a;
LOG(("%04x: PIA%d read DDR A = %02X\n", activecpu_get_previouspc(), which, val));
}
break;
/******************* port B output/DDR read *******************/
case PIA_DDRB:
/* read output register */
if (OUTPUT_SELECTED(p->ctl_b))
{
/* update the input */
if ((FPTR)(p->intf->in_b_func) > 0x100)
p->in_b = p->intf->in_b_func(0);
#ifdef MAME_DEBUG
else if ((p->ddr_b ^ 0xff) && !(p->in_set & PIA_IN_SET_B)) {
logerror("PIA%d: Error! no port B read handler. Three-state pins %02x are undefined\n",
which, p->ddr_b ^ 0xff);
p->in_set |= PIA_IN_SET_B; // disable logging
}
#endif // MAME_DEBUG
/* combine input and output values */
val = (p->out_b & p->ddr_b) + (p->in_b & ~p->ddr_b);
/* IRQ flags implicitly cleared by a read */
p->irq_b1 = p->irq_b2 = 0;
update_6821_interrupts(p);
LOG(("%04x: PIA%d read port B = %02X\n", activecpu_get_previouspc(), which, val));
}
/* read DDR register */
else
{
val = p->ddr_b;
LOG(("%04x: PIA%d read DDR B = %02X\n", activecpu_get_previouspc(), which, val));
}
break;
/******************* port A control read *******************/
case PIA_CTLA:
/* Update CA1 & CA2 if callback exists, these in turn may update IRQ's */
if ((FPTR)(p->intf->in_ca1_func) > 0x100)
pia_set_input_ca1(which, p->intf->in_ca1_func(0));
#ifdef MAME_DEBUG
else if (!(p->in_set & PIA_IN_SET_CA1)) {
logerror("PIA%d: Warning! no CA1 read handler. Assuming pin not connected\n",which);
p->in_set |= PIA_IN_SET_CA1; // disable logging
}
#endif // MAME_DEBUG
if ((FPTR)(p->intf->in_ca2_func) > 0x100)
pia_set_input_ca2(which, p->intf->in_ca2_func(0));
#ifdef MAME_DEBUG
else if (C2_INPUT(p->ctl_a) && !(p->in_set & PIA_IN_SET_CA2)) {
logerror("PIA%d: Warning! no CA2 read handler. Assuming pin not connected\n",which);
p->in_set |= PIA_IN_SET_CA2; // disable logging
}
#endif // MAME_DEBUG
/* read control register */
val = p->ctl_a;
/* set the IRQ flags if we have pending IRQs */
if (p->irq_a1) val |= PIA_IRQ1;
if (p->irq_a2 && C2_INPUT(p->ctl_a)) val |= PIA_IRQ2;
LOG(("%04x: PIA%d read control A = %02X\n", activecpu_get_previouspc(), which, val));
break;
/******************* port B control read *******************/
case PIA_CTLB:
/* Update CB1 & CB2 if callback exists, these in turn may update IRQ's */
if ((FPTR)(p->intf->in_cb1_func) > 0x100)
pia_set_input_cb1(which, p->intf->in_cb1_func(0));
#ifdef MAME_DEBUG
else if (!(p->in_set & PIA_IN_SET_CB1)) {
logerror("PIA%d: Error! no CB1 read handler. Three-state pin is undefined\n",which);
p->in_set |= PIA_IN_SET_CB1; // disable logging
}
#endif // MAME_DEBUG
if ((FPTR)(p->intf->in_cb2_func) > 0x100)
pia_set_input_cb2(which, p->intf->in_cb2_func(0));
#ifdef MAME_DEBUG
else if (C2_INPUT(p->ctl_b) && !(p->in_set & PIA_IN_SET_CB2)) {
logerror("PIA%d: Error! no CB2 read handler. Three-state pin is undefined\n",which);
p->in_set |= PIA_IN_SET_CB2; // disable logging
}
#endif // MAME_DEBUG
/* read control register */
val = p->ctl_b;
/* set the IRQ flags if we have pending IRQs */
if (p->irq_b1) val |= PIA_IRQ1;
if (p->irq_b2 && C2_INPUT(p->ctl_b)) val |= PIA_IRQ2;
LOG(("%04x: PIA%d read control B = %02X\n", activecpu_get_previouspc(), which, val));
break;
}
return val;
}
void C6821::Write(BYTE byRS, BYTE byData)
{
byRS &= 3;
switch( byRS )
{
/******************* port A output/DDR write *******************/
case PIA_DDRA:
// write output register
if ( OUTPUT_SELECTED( m_byCTLA ) )
{
// update the output value
m_byOA = byData;
// send it to the output function
if ( m_byDDRA )
PIA_W_CALLBACK( m_stOutA, m_byOA & m_byDDRA );
}
// write DDR register
else
{
if ( m_byDDRA != byData )
{
m_byDDRA = byData;
// send it to the output function
if ( m_byDDRA )
PIA_W_CALLBACK( m_stOutA, m_byOA & m_byDDRA );
}
}
break;
/******************* port B output/DDR write *******************/
case PIA_DDRB:
// write output register
if ( OUTPUT_SELECTED( m_byCTLB ) )
{
// update the output value
m_byOB = byData;
// send it to the output function
if ( m_byDDRB )
PIA_W_CALLBACK( m_stOutB, m_byOB & m_byDDRB );
// CB2 is configured as output and in write strobe mode
if ( C2_OUTPUT( m_byCTLB ) && C2_STROBE_MODE( m_byCTLB ) )
{
// this will cause a transition low; call the output function if we're currently high
if ( m_byOCB2 )
PIA_W_CALLBACK( m_stOutCB2, 0 );
m_byOCB2 = 0;
// if the CB2 strobe is cleared by the E, reset it right away
if ( STROBE_E_RESET( m_byCTLB ) )
{
PIA_W_CALLBACK( m_stOutCB2, 1 );
m_byOCB2 = 1;
}
}
}
// write DDR register
else
{
if ( m_byDDRB != byData )
{
m_byDDRB = byData;
// send it to the output function
if ( m_byDDRB )
PIA_W_CALLBACK( m_stOutB, m_byOB & m_byDDRB );
}
}
break;
/******************* port A control write *******************/
case PIA_CTLA:
// Bit 7 and 6 read only
byData &= 0x3f;
// CA2 is configured as output and in set/reset mode
if ( C2_OUTPUT( byData ) )
{
// determine the new value
int temp = SET_C2( byData ) ? 1 : 0;
// if this creates a transition, call the CA2 output function
if ( m_byOCA2 ^ temp)
PIA_W_CALLBACK( m_stOutCA2, temp );
// set the new value
m_byOCA2 = temp;
}
// update the control register
m_byCTLA = ( m_byCTLA & ~0x3F ) | byData;
// update externals
UpdateInterrupts();
break;
/******************* port B control write *******************/
case PIA_CTLB:
/* Bit 7 and 6 read only - PD 16/01/00 */
byData &= 0x3f;
// CB2 is configured as output and in set/reset mode
if ( C2_OUTPUT( byData ) )
{
// determine the new value
int temp = SET_C2( byData ) ? 1 : 0;
// if this creates a transition, call the CA2 output function
if ( m_byOCB2 ^ temp)
PIA_W_CALLBACK( m_stOutCB2, temp );
// set the new value
m_byOCB2 = temp;
}
// update the control register
m_byCTLB = ( m_byCTLB & ~0x3F ) | byData;
// update externals
UpdateInterrupts();
break;
}
}
BYTE C6821::Read(BYTE byRS)
{
BYTE retval = 0;
byRS &= 3;
switch ( byRS )
{
/******************* port A output/DDR read *******************/
case PIA_DDRA:
// read output register
if ( OUTPUT_SELECTED(m_byCTLA) )
{
// combine input and output values
retval = ( m_byOA & m_byDDRA ) | ( m_byIA & ~m_byDDRA );
// IRQ flags implicitly cleared by a read
CLEAR_IRQ1( m_byCTLA );
CLEAR_IRQ1( m_byCTLB );
UpdateInterrupts();
// CA2 is configured as output and in read strobe mode
if ( C2_OUTPUT(m_byCTLA) && C2_STROBE_MODE(m_byCTLA) )
{
// this will cause a transition low; call the output function if we're currently high
if ( m_byOCA2 )
PIA_W_CALLBACK( m_stOutCA2, 0 );
m_byOCA2 = 0;
// if the CA2 strobe is cleared by the E, reset it right away
if ( STROBE_E_RESET( m_byCTLA ) )
{
PIA_W_CALLBACK( m_stOutCA2, 1 );
m_byOCA2 = 1;
}
}
}
// read DDR register
else
{
retval = m_byDDRA;
}
break;
/******************* port B output/DDR read *******************/
case PIA_DDRB:
// read output register
if ( OUTPUT_SELECTED( m_byCTLB ) )
{
// combine input and output values
retval = ( m_byOB & m_byDDRB ) + ( m_byIB & ~m_byDDRB );
// IRQ flags implicitly cleared by a read
CLEAR_IRQ2( m_byCTLA );
CLEAR_IRQ2( m_byCTLB );
UpdateInterrupts();
}
/* read DDR register */
else
{
retval = m_byDDRB;
}
break;
/******************* port A control read *******************/
case PIA_CTLA:
// read control register
retval = m_byCTLA;
// when CA2 is an output, IRQA2 = 0, and is not affected by CA2 transitions.
if ( C2_OUTPUT( m_byCTLA ) )
retval &= ~PIA_IRQ2;
break;
/******************* port B control read *******************/
case PIA_CTLB:
retval = m_byCTLB;
// when CB2 is an output, IRQB2 = 0, and is not affected by CB2 transitions.
if ( C2_OUTPUT( m_byCTLB ) )
retval &= ~PIA_IRQ2;
break;
}
return retval;
}