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amiga/agnus_copper: handle SKIP properly

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This commit is contained in:
angelosa 2025-01-10 10:06:13 +01:00
parent bab78a2320
commit fe1b9eac21
2 changed files with 21 additions and 15 deletions
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35
src/mame/amiga/agnus_copper.cpp
View File

@ -92,6 +92,7 @@ void agnus_copper_device::device_start()
save_item(NAME(m_pc));
save_item(NAME(m_state_waiting));
save_item(NAME(m_state_waitblit));
save_item(NAME(m_state_skipping));
save_item(NAME(m_waitval));
save_item(NAME(m_waitmask));
save_item(NAME(m_pending_data));
@ -202,6 +203,7 @@ inline void agnus_copper_device::set_pc(u8 ch, bool is_sync)
{
m_pc = m_lc[ch];
m_state_waiting = false;
m_state_skipping = false;
LOGPC("%s: COPJMP%d new PC = %08x%s\n"
, machine().describe_context()
, ch + 1
@ -309,6 +311,17 @@ int agnus_copper_device::execute_next(int xpos, int ypos, bool is_blitter_busy,
word0 = (word0 >> 1) & 0xff;
if (word0 >= m_cdang_setting)
{
// SKIP applies to valid MOVEs only
// - apocalyps (gameplay)
if (m_state_skipping)
{
LOGINST(" (Ignored)\n");
m_state_skipping = false;
// TODO: verify timings
// may depend on num of planes enabled (move_offset) or opcode fetch above is enough.
xpos += COPPER_CYCLES_TO_PIXELS(2);
return xpos;
}
// delay write to the next available DMA slot if not in blanking area
// - bchvolly (title), suprfrog & abreed (bottom playfield rows)
const bool horizontal_blank = xpos < 0x47;
@ -328,6 +341,7 @@ int agnus_copper_device::execute_next(int xpos, int ypos, bool is_blitter_busy,
m_waitmask = 0xffff;
m_state_waitblit = false;
m_state_waiting = true;
m_state_skipping = false;
return 511;
}
@ -354,6 +368,7 @@ int agnus_copper_device::execute_next(int xpos, int ypos, bool is_blitter_busy,
wait_offset
);
m_state_skipping = false;
m_state_waiting = true;
xpos += COPPER_CYCLES_TO_PIXELS(wait_offset);
}
@ -362,25 +377,15 @@ int agnus_copper_device::execute_next(int xpos, int ypos, bool is_blitter_busy,
else
{
int curpos = (ypos << 8) | (xpos >> 1);
m_state_skipping = ((curpos & m_waitmask) >= (m_waitval & m_waitmask)
&& (!m_state_waitblit || !(is_blitter_busy)));
LOGINST(" SKIP %04x & %04x (currently %04x)\n",
LOGINST(" SKIP %04x & %04x (currently %04x) - %s\n",
m_waitval,
m_waitmask,
(ypos << 8) | (xpos >> 1)
(ypos << 8) | (xpos >> 1),
m_state_skipping ? "Skipping" : "Not skipped"
);
/* if we're past the wait time, stop it and hold up 2 cycles */
if ((curpos & m_waitmask) >= (m_waitval & m_waitmask) &&
(!m_state_waitblit || !(is_blitter_busy)))
{
LOGINST(" Skipped\n");
/* count the cycles it out have taken to fetch the next instruction */
// TODO: look ahead, check if next instruction is a valid MOVE
// SKIP/WAIT and illegal instructions aren't skipped.
m_pc += 4;
xpos += COPPER_CYCLES_TO_PIXELS(2);
}
}
}

1
src/mame/amiga/agnus_copper.h
View File

@ -63,6 +63,7 @@ private:
// internal state
bool m_state_waiting;
bool m_state_skipping;
bool m_state_waitblit;
u16 m_waitval;
u16 m_waitmask;