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atari/gtia.cpp: fix readback of undocumented read registers, fix consol direction readback, better cold boot initial values

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* fixes Acid800 "GTIA: default value" and "GTIA: CONSOL test" items
This commit is contained in:
angelosa 2022-10-08 20:12:25 +02:00
parent 8cff67755c
commit a6b5542362
2 changed files with 46 additions and 27 deletions
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69
src/mame/atari/gtia.cpp
View File

@ -164,7 +164,7 @@ void gtia_device::device_start()
save_item(NAME(m_r.gtia1c));
save_item(NAME(m_r.gtia1d));
save_item(NAME(m_r.gtia1e));
save_item(NAME(m_r.cons));
save_item(NAME(m_r.consol));
save_item(NAME(m_w.hposp0));
save_item(NAME(m_w.hposp1));
@ -197,7 +197,7 @@ void gtia_device::device_start()
save_item(NAME(m_w.vdelay));
save_item(NAME(m_w.gractl));
save_item(NAME(m_w.hitclr));
save_item(NAME(m_w.cons));
save_item(NAME(m_w.consol));
save_item(NAME(m_h.grafp0));
save_item(NAME(m_h.grafp1));
@ -251,24 +251,36 @@ void gtia_device::device_reset()
m_lumpf1 = 0;
/* reset the GTIA read/write/helper registers */
for (int i = 0; i < 32; i++)
write(i, 0);
if (is_ntsc())
m_r.pal = 0xff;
else
m_r.pal = 0xf1;
m_r.gtia15 = 0xff;
m_r.gtia16 = 0xff;
m_r.gtia17 = 0xff;
m_r.gtia18 = 0xff;
m_r.gtia19 = 0xff;
m_r.gtia1a = 0xff;
m_r.gtia1b = 0xff;
m_r.gtia1c = 0xff;
m_r.gtia1d = 0xff;
m_r.gtia1e = 0xff;
m_r.cons = 0x07; /* console keys */
// Altirra observed values on real HW
// initial state for w/o regs marked as undefined
const u8 cold_start_values[32] = {
// m*pf p*pf
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
// m*pl p*pl
0x0f, 0x0f, 0x0f, 0x0f, 0x0e, 0x0d, 0x0b, 0x07,
// trig* <undefined>
0x01, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00,
// <undefined> <undefined>
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};
for (int i = 0; i < 32; i++)
write(i, cold_start_values[i]);
m_r.pal = is_ntsc() ? 0x0f : 0x01;
m_r.gtia15 = 0x0f;
m_r.gtia16 = 0x0f;
m_r.gtia17 = 0x0f;
m_r.gtia18 = 0x0f;
m_r.gtia19 = 0x0f;
m_r.gtia1a = 0x0f;
m_r.gtia1b = 0x0f;
m_r.gtia1c = 0x0f;
m_r.gtia1d = 0x0f;
m_r.gtia1e = 0x0f;
/* set consol default dir with all lines r/o */
m_r.consol = 0x00;
m_w.consol = 0x00;
SETCOL_B(ILL, 0x3e); /* bright red */
SETCOL_B(EOR, 0xff); /* yellow */
@ -355,10 +367,17 @@ uint8_t gtia_device::read(offs_t offset)
case 30: return m_r.gtia1e;
case 31:
m_r.cons = !m_read_cb.isnull() ? (m_read_cb(0) & 0x0f) : 0x00;
return m_r.cons;
{
// unconfirmed behaviour with reading lines unconnected,
// assume active low logic with read direction.
const u8 consol_read_dir = (~m_w.consol & 0xf);
const u8 res = !m_read_cb.isnull() ? m_read_cb(0) : 0x0f;
m_r.consol = res & consol_read_dir;
return m_r.consol;
}
}
return 0xff;
// unreachable
return 0x0f;
}
@ -875,11 +894,11 @@ void gtia_device::write(offs_t offset, uint8_t data)
break;
case 31: /* write console (speaker) */
if (data == m_w.cons)
if (data == m_w.consol)
break;
m_w.cons = data;
m_w.consol = data & 0x0f;
if (!m_write_cb.isnull())
m_write_cb((offs_t)0, m_w.cons);
m_write_cb((offs_t)0, m_w.consol);
break;
}
}

4
src/mame/atari/gtia.h
View File

@ -101,7 +101,7 @@ private:
uint8_t gtia1c; /* d01c nothing */
uint8_t gtia1d; /* d01d nothing */
uint8_t gtia1e; /* d01e nothing */
uint8_t cons; /* d01f console keys */
uint8_t consol; /* d01f console keys */
};
/* writing registers */
@ -138,7 +138,7 @@ private:
uint8_t vdelay; /* d01c delay until vertical retrace */
uint8_t gractl; /* d01d graphics control */
uint8_t hitclr; /* d01e clear collisions */
uint8_t cons; /* d01f write console (speaker) */
uint8_t consol; /* d01f write console (speaker) */
};
/* helpers */