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// license:BSD-3-Clause
// copyright-holders:Fabio Priuli
/***************************************************************************
Atari 2600 cart with DPC chip (Pitfall II)
***************************************************************************/
#include "emu.h"
#include "dpc.h"
// DPC device
const device_type ATARI_DPC = &device_creator<dpc_device>;
dpc_device::dpc_device(const machine_config& mconfig, const char* tag, device_t* owner, uint32_t clock) :
device_t(mconfig, ATARI_DPC, "Atari DCP", tag, owner, clock, "atari_dcp", __FILE__),
m_movamt(0),
m_latch_62(0),
m_latch_64(0),
m_dlc(0),
m_shift_reg(0),
m_displaydata(nullptr),
m_oscillator(nullptr)
{
}
void dpc_device::device_start()
{
m_oscillator = timer_alloc(TIMER_OSC);
m_oscillator->reset();
for (int i = 0; i < 8; i++)
{
save_item(NAME(m_df[i].top), i);
save_item(NAME(m_df[i].bottom), i);
save_item(NAME(m_df[i].low), i);
save_item(NAME(m_df[i].high), i);
save_item(NAME(m_df[i].flag), i);
save_item(NAME(m_df[i].music_mode), i);
save_item(NAME(m_df[i].osc_clk), i);
}
save_item(NAME(m_movamt));
save_item(NAME(m_latch_62));
save_item(NAME(m_latch_64));
save_item(NAME(m_dlc));
save_item(NAME(m_shift_reg));
}
void dpc_device::device_reset()
{
for (auto & elem : m_df)
{
elem.osc_clk = 0;
elem.flag = 0;
elem.music_mode = 0;
}
m_oscillator->adjust(attotime::from_hz(18400), 0, attotime::from_hz(18400));
}
void dpc_device::check_flag(uint8_t data_fetcher)
{
/* Set flag when low counter equals top */
if (m_df[data_fetcher].low == m_df[data_fetcher].top)
m_df[data_fetcher].flag = 1;
/* Reset flag when low counter equals bottom */
if (m_df[data_fetcher].low == m_df[data_fetcher].bottom)
m_df[data_fetcher].flag = 0;
}
void dpc_device::decrement_counter(uint8_t data_fetcher)
{
m_df[data_fetcher].low -= 1;
if (m_df[data_fetcher].low == 0xff)
{
m_df[data_fetcher].high -= 1;
if (data_fetcher > 4 && m_df[data_fetcher].music_mode)
m_df[data_fetcher].low = m_df[data_fetcher].top;
}
check_flag(data_fetcher);
}
//-------------------------------------------------
// device_timer - handler timer events
//-------------------------------------------------
void dpc_device::device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr)
{
if (id == TIMER_OSC)
{
// callback
for (int data_fetcher = 5; data_fetcher < 8; data_fetcher++)
{
if (m_df[data_fetcher].osc_clk)
{
decrement_counter(data_fetcher);
}
}
}
}
//-------------------------------------------------
// Read / Write accesses
//-------------------------------------------------
READ8_MEMBER(dpc_device::read)
{
static const uint8_t dpc_amplitude[8] = { 0x00, 0x04, 0x05, 0x09, 0x06, 0x0a, 0x0b, 0x0f };
uint8_t data_fetcher = offset & 0x07;
uint8_t data = 0xff;
//logerror("%04X: Read from DPC offset $%02X\n", machine().device<cpu_device>("maincpu")->pc(), offset);
if (offset < 0x08)
{
switch(offset & 0x06)
{
case 0x00: // Random number generator
case 0x02:
return m_shift_reg;
case 0x04: // Sound value, MOVAMT value AND'd with Draw Line Carry; with Draw Line Add
m_latch_62 = m_latch_64;
case 0x06: // Sound value, MOVAMT value AND'd with Draw Line Carry; without Draw Line Add
m_latch_64 = m_latch_62 + m_df[4].top;
m_dlc = (m_latch_62 + m_df[4].top > 0xff) ? 1 : 0;
data = 0;
if (m_df[5].music_mode && m_df[5].flag)
data |= 0x01;
if (m_df[6].music_mode && m_df[6].flag)
data |= 0x02;
if (m_df[7].music_mode && m_df[7].flag)
data |= 0x04;
return (m_dlc ? m_movamt & 0xf0 : 0) | dpc_amplitude[data];
}
}
else
{
uint8_t display_data = m_displaydata[(~((m_df[data_fetcher].low | (m_df[data_fetcher].high << 8))) & 0x7ff)];
switch (offset & 0x38)
{
case 0x08: // display data
data = display_data;
break;
case 0x10: // display data AND'd w/flag
data = m_df[data_fetcher].flag ? display_data : 0x00;
break;
case 0x18: // display data AND'd w/flag, nibbles swapped
data = m_df[data_fetcher].flag ? BITSWAP8(display_data,3,2,1,0,7,6,5,4) : 0x00;
break;
case 0x20: // display data AND'd w/flag, byte reversed
data = m_df[data_fetcher].flag ? BITSWAP8(display_data,0,1,2,3,4,5,6,7) : 0x00;
break;
case 0x28: // display data AND'd w/flag, rotated right
data = m_df[data_fetcher].flag ? (display_data >> 1) : 0x00;
break;
case 0x30: // display data AND'd w/flag, rotated left
data = m_df[data_fetcher].flag ? (display_data << 1) : 0x00;
break;
case 0x38: // flag
data = m_df[data_fetcher].flag ? 0xff : 0x00;
break;
}
if (data_fetcher < 5 || !m_df[data_fetcher].osc_clk)
{
decrement_counter(data_fetcher);
}
}
return data;
}
WRITE8_MEMBER(dpc_device::write)
{
uint8_t data_fetcher = offset & 0x07;
switch (offset & 0x38)
{
case 0x00: // Top count
m_df[data_fetcher].top = data;
m_df[data_fetcher].flag = 0;
check_flag(data_fetcher);
break;
case 0x08: // Bottom count
m_df[data_fetcher].bottom = data;
check_flag(data_fetcher);
break;
case 0x10: // Counter low
m_df[data_fetcher].low = data;
if (data_fetcher == 4)
m_latch_64 = data;
if (data_fetcher > 4 && m_df[data_fetcher].music_mode)
m_df[data_fetcher].low = m_df[data_fetcher].top;
check_flag(data_fetcher);
break;
case 0x18: // Counter high
m_df[data_fetcher].high = data;
m_df[data_fetcher].music_mode = data & 0x10;
m_df[data_fetcher].osc_clk = data & 0x20;
if (data_fetcher > 4 && m_df[data_fetcher].music_mode && m_df[data_fetcher].low == 0xff)
{
m_df[data_fetcher].low = m_df[data_fetcher].top;
check_flag(data_fetcher);
}
break;
case 0x20: // Draw line movement value / MOVAMT
m_movamt = data;
break;
case 0x28: // Not used
logerror("%04X: Write to unused DPC register $%02X, data $%02X\n", machine().device<cpu_device>("maincpu")->pc(), offset, data);
break;
case 0x30: // Random number generator reset
m_shift_reg = 0;
break;
case 0x38: // Not used
logerror("%04X: Write to unused DPC register $%02X, data $%02X\n", machine().device<cpu_device>("maincpu")->pc(), offset, data);
break;
}
}
// cart device
const device_type A26_ROM_DPC = &device_creator<a26_rom_dpc_device>;
a26_rom_dpc_device::a26_rom_dpc_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
: a26_rom_f8_device(mconfig, A26_ROM_DPC, "Atari 2600 ROM Cart Pitfall II", tag, owner, clock, "a2600_dcp", __FILE__),
m_dpc(*this, "dpc")
{
}
//-------------------------------------------------
// mapper specific start/reset
//-------------------------------------------------
void a26_rom_dpc_device::device_start()
{
save_item(NAME(m_base_bank));
}
void a26_rom_dpc_device::device_reset()
{
m_base_bank = 0;
}
void a26_rom_dpc_device::setup_addon_ptr(uint8_t *ptr)
{
m_dpc->set_display_data(ptr);
}
static MACHINE_CONFIG_FRAGMENT( a26_dpc )
MCFG_DEVICE_ADD("dpc", ATARI_DPC, 0)
MACHINE_CONFIG_END
machine_config_constructor a26_rom_dpc_device::device_mconfig_additions() const
{
return MACHINE_CONFIG_NAME( a26_dpc );
}
READ8_MEMBER(a26_rom_dpc_device::read_rom)
{
if (offset < 0x40)
return m_dpc->read(space, offset);
else
return a26_rom_f8_device::read_rom(space, offset);
}
WRITE8_MEMBER(a26_rom_dpc_device::write_bank)
{
if (offset >= 0x40 && offset < 0x80)
m_dpc->write(space, offset, data);
else
a26_rom_f8_device::write_bank(space, offset, data);
}
DIRECT_UPDATE_MEMBER(a26_rom_dpc_device::cart_opbase)
{
if (!machine().debugger_access())
{
uint8_t new_bit;
new_bit = (m_dpc->m_shift_reg & 0x80) ^ ((m_dpc->m_shift_reg & 0x20) << 2);
new_bit = new_bit ^ (((m_dpc->m_shift_reg & 0x10) << 3) ^ ((m_dpc->m_shift_reg & 0x08) << 4));
new_bit = new_bit ^ 0x80;
m_dpc->m_shift_reg = new_bit | (m_dpc->m_shift_reg >> 1);
}
return address;
}
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