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// license:BSD-3-Clause
// copyright-holders:Mike Harris, Aaron Giles
/***************************************************************************
Namco 06XX
This chip is used as an interface to up to 4 other custom chips.
It signals IRQs to the custom MCUs when writes happen, and generates
NMIs to the controlling CPU to drive reads based on a clock.
It uses a clock divider that's used to pulse the NMI and custom chip select
lines.
The control register controls chip as such: the low 4 bits are chip selects
(active high), the 5th bit is read/!write, and the upper 3 bits are the
clock divide.
SD0-SD7 are data I/O lines connecting to the controlling CPU
SEL selects either control (1) or data (0), usually connected to
an address line of the controlling CPU
/NMI is an NMI signal line for the controlling CPU
ID0-ID7 are data I/O lines connecting to the other custom chips
/IO1-/IO4 are IRQ signal lines for each custom chip
+------+
[1]|1 28|Vcc
ID7|2 27|SD7
ID6|3 26|SD6
ID5|4 25|SD5
ID4|5 24|SD4
ID3|6 23|SD3
ID2|7 22|SD2
ID1|8 21|SD1
ID0|9 20|SD0
/IO1|10 19|/NMI
/IO2|11 18|/CS
/IO3|12 17|CLOCK
/IO4|13 16|R/W
GND|14 15|SEL
+------+
[1] on polepos, galaga, xevious, and bosco: connected to K3 of the 51xx
on bosco and xevious, connected to R8 of the 50xx
Note that Xevious has a potential race condition at 0xE9. It checks if
the control register is 0x10 (chip disabled), then 4 instructions later
acts on that check. If an NMI occurs between, it can crash.
06XX interface:
---------------
Galaga 51XX ---- ---- 54XX
Bosconian (CPU board) 51XX ---- 50XX 54XX
Bosconian (Video board) 50XX 52XX ---- ----
Xevious 51XX ---- 50XX 54XX
Dig Dug 51XX 53XX ---- ----
Pole Position / PP II 51XX 53XX 52XX 54XX
Galaga writes:
control = 10(000), data = FF at startup
control = 71(011), read 3, control = 10
control = A1(101), write 4, control = 10
control = A8(101), write 12, control = 10
Xevious writes:
control = 10 at startup
control = A1(101), write 6, control = 10
control = 71(011), read 3, control = 10
control = 64(011), write 1, control = 10
control = 74(011), read 4, control = 10
control = 68(011), write 7, control = 10
Dig Dug writes:
control = 10(000), data = 10 at startup
control = A1(101), write 3, control = 10
control = 71(011), read 3, control = 10
control = D2(110), read 2, control = 10
Bosco writes:
control = 10(000), data = FF at startup
control = C8(110), write 17, control = 10
control = 61(011), write 1, control = 10
control = 71(011), read 3, control = 10
control = 94(100), read 4, control = 10
control = 64(011), write 1, control = 10
control = 84(100), write 5, control = 10
control = 34(001), write 1, control = 10
***************************************************************************/
#include "emu.h"
#include "machine/namco06.h"
#define VERBOSE 0
#include "logmacro.h"
TIMER_CALLBACK_MEMBER( namco_06xx_device::nmi_generate )
{
// This timer runs at twice the clock, since we do work on both the
// rising and falling edge.
//
// During reads, the first NMI pulse is supressed to give the chip a
// cycle to write.
//
// If the control register is written while CS is asserted, RW won't be
// changed until the next rising edge.
if (m_rw_change && m_next_timer_state)
{
if (!m_rw_stretch)
{
m_rw[0](0, BIT(m_control, 4));
m_rw[1](0, BIT(m_control, 4));
m_rw[2](0, BIT(m_control, 4));
m_rw[3](0, BIT(m_control, 4));
m_rw_change = false;
}
}
if (m_next_timer_state && !m_nmi_stretch )
{
set_nmi(ASSERT_LINE);
}
else
{
set_nmi(CLEAR_LINE);
}
m_chipsel[0](0, BIT(m_control, 0) && m_next_timer_state);
m_chipsel[1](0, BIT(m_control, 1) && m_next_timer_state);
m_chipsel[2](0, BIT(m_control, 2) && m_next_timer_state);
m_chipsel[3](0, BIT(m_control, 3) && m_next_timer_state);
m_next_timer_state = !m_next_timer_state;
m_nmi_stretch = false;
m_rw_stretch = false;
}
uint8_t namco_06xx_device::data_r(offs_t offset)
{
uint8_t result = 0xff;
if (!BIT(m_control, 4))
{
logerror("%s: 06XX '%s' read in write mode %02x\n",machine().describe_context(),tag(),m_control);
return 0;
}
if (BIT(m_control, 0)) result &= m_read[0](0);
if (BIT(m_control, 1)) result &= m_read[1](0);
if (BIT(m_control, 2)) result &= m_read[2](0);
if (BIT(m_control, 3)) result &= m_read[3](0);
return result;
}
void namco_06xx_device::data_w(offs_t offset, uint8_t data)
{
if (BIT(m_control, 4))
{
logerror("%s: 06XX '%s' write in read mode %02x\n",machine().describe_context(),tag(),m_control);
return;
}
if (BIT(m_control, 0)) m_write[0](0, data);
if (BIT(m_control, 1)) m_write[1](0, data);
if (BIT(m_control, 2)) m_write[2](0, data);
if (BIT(m_control, 3)) m_write[3](0, data);
}
uint8_t namco_06xx_device::ctrl_r()
{
return m_control;
}
void namco_06xx_device::ctrl_w(uint8_t data)
{
m_control = data;
// The upper 3 control bits are the clock divider.
if ((m_control & 0xe0) == 0)
{
m_nmi_timer->adjust(attotime::never);
set_nmi(CLEAR_LINE);
m_chipsel[0](0, CLEAR_LINE);
m_chipsel[1](0, CLEAR_LINE);
m_chipsel[2](0, CLEAR_LINE);
m_chipsel[3](0, CLEAR_LINE);
// Setting this to true makes the next RW change not stretch.
m_next_timer_state = true;
}
else
{
m_rw_stretch = !m_next_timer_state;
m_rw_change = true;
m_next_timer_state = true;
m_nmi_stretch = BIT(m_control, 4);
// NMI is cleared immediately if its to be stretched.
if (m_nmi_stretch) set_nmi(CLEAR_LINE);
uint8_t num_shifts = (m_control & 0xe0) >> 5;
uint8_t divisor = 1 << num_shifts;
// The next change should happen on the next clock falling edge.
// Xevious' race causes this to bootloopsif it isn't 0.
m_nmi_timer->adjust(attotime::zero, 0, attotime::from_hz(clock() / divisor) / 2);
}
}
void namco_06xx_device::set_nmi(int state)
{
if (!m_nmicpu->suspended(SUSPEND_REASON_HALT | SUSPEND_REASON_RESET | SUSPEND_REASON_DISABLE))
{
m_nmicpu->set_input_line(INPUT_LINE_NMI, state);
}
}
DEFINE_DEVICE_TYPE(NAMCO_06XX, namco_06xx_device, "namco06", "Namco 06xx")
namco_06xx_device::namco_06xx_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
: device_t(mconfig, NAMCO_06XX, tag, owner, clock)
, m_control(0)
, m_next_timer_state(false)
, m_nmi_stretch(false)
, m_rw_stretch(false)
, m_rw_change(false)
, m_nmicpu(*this, finder_base::DUMMY_TAG)
, m_chipsel(*this)
, m_rw(*this)
, m_read(*this)
, m_write(*this)
{
}
//-------------------------------------------------
// device_start - device-specific startup
//-------------------------------------------------
void namco_06xx_device::device_start()
{
m_chipsel.resolve_all_safe();
m_rw.resolve_all_safe();
m_read.resolve_all_safe(0xff);
m_write.resolve_all_safe();
/* allocate a timer */
m_nmi_timer = machine().scheduler().timer_alloc(timer_expired_delegate(FUNC(namco_06xx_device::nmi_generate),this));
save_item(NAME(m_control));
save_item(NAME(m_next_timer_state));
save_item(NAME(m_nmi_stretch));
save_item(NAME(m_rw_stretch));
save_item(NAME(m_rw_change));
}
//-------------------------------------------------
// device_reset - device-specific reset
//-------------------------------------------------
void namco_06xx_device::device_reset()
{
m_control = 0;
}
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