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C64: [VIC2] implement sprite enables as described in the VICII article

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This commit is contained in:
Gyorgy Szombathelyi
2020-03-21 22:45:09 +01:00
parent 11679a3e2b
commit 4914310668
1 changed files with 129 additions and 74 deletions
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203
cores/c64/rtl/video_vicII_656x_a.vhd
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@@ -168,10 +168,17 @@ architecture rtl of video_vicii_656x is
-- Sprite work registers
signal MPtr : unsigned(7 downto 0); -- sprite base pointer
signal MPixels : MPixelsDef; -- Sprite 24 bit shift register
signal MActive : MFlags; -- Sprite is active (derived from MCnt)
signal MActive : MFlags; -- Sprite is active
signal MActive_next : MFlags; -- Sprite is active
signal MDMA : MFlags; -- Sprite DMA is enabled
signal MDMA_next : MFlags; -- Sprite DMA is enabled
signal MCnt : MCntDef;
signal MCnt_next : MCntDef;
signal MCBase : MCntDef;
signal MCBase_next : MCntDef;
signal MXE_ff : unsigned(7 downto 0); -- Sprite X expansion flipflop
signal MYE_ff : unsigned(7 downto 0); -- Sprite Y expansion flipflop
signal MYE_ff_next : unsigned(7 downto 0); -- Sprite Y expansion flipflop
signal MC_ff : unsigned(7 downto 0); -- controls sprite shift-register in multicolor
signal MShift : MFlags; -- Sprite is shifting
signal MCurrentPixel : MCurrentPixelDef;
@@ -408,7 +415,7 @@ vicStateMachine: process(clk)
and enaData = '1'
and vicCycle = cycleSpriteA then
MPtr <= (others => '1');
if MActive(to_integer(sprite)) then
if MActive_next(to_integer(sprite)) then
MPtr <= di;
end if;
@@ -540,28 +547,28 @@ vicStateMachine: process(clk)
baSprite37 <= '1';
end if;
if MActive(0) and (vicCycle = cycleCalcSprites) then
if MDMA_next(0) and (vicCycle = cycleCalcSprites) then
baSprite04 <= '0';
end if;
if MActive(1) and (vicCycle = cycleSpriteBa2) then
if MDMA(1) and (vicCycle = cycleSpriteBa2) then
baSprite15 <= '0';
end if;
if MActive(2) and (vicCycle = cycleSpriteB) and (sprite = 0) then
if MDMA(2) and (vicCycle = cycleSpriteB) and (sprite = 0) then
baSprite26 <= '0';
end if;
if MActive(3) and (vicCycle = cycleSpriteB) and (sprite = 1) then
if MDMA(3) and (vicCycle = cycleSpriteB) and (sprite = 1) then
baSprite37 <= '0';
end if;
if MActive(4) and (vicCycle = cycleSpriteB) and (sprite = 2) then
if MDMA(4) and (vicCycle = cycleSpriteB) and (sprite = 2) then
baSprite04 <= '0';
end if;
if MActive(5) and (vicCycle = cycleSpriteB) and (sprite = 3) then
if MDMA(5) and (vicCycle = cycleSpriteB) and (sprite = 3) then
baSprite15 <= '0';
end if;
if MActive(6) and (vicCycle = cycleSpriteB) and (sprite = 4) then
if MDMA(6) and (vicCycle = cycleSpriteB) and (sprite = 4) then
baSprite26 <= '0';
end if;
if MActive(7) and (vicCycle = cycleSpriteB) and (sprite = 5) then
if MDMA(7) and (vicCycle = cycleSpriteB) and (sprite = 5) then
baSprite37 <= '0';
end if;
end if;
@@ -940,82 +947,130 @@ calcBitmap: process(clk)
end if;
end process;
-- -----------------------------------------------------------------------
-- Which sprites are active?
-- -----------------------------------------------------------------------
process(MCnt)
begin
for i in 0 to 7 loop
MActive(i) <= false;
if MCnt(i) /= 63 then
MActive(i) <= true;
end if;
end loop;
end process;
-- -----------------------------------------------------------------------
-- Sprite byte counter
-- Y expansion flipflop
-- -----------------------------------------------------------------------
process(rasterY, MDMA, MCnt, MCBase, MActive, MYE_ff, ME, MY, MYE, vicCycle, sprite)
begin
MCBase_next <= MCBase;
MDMA_next <= MDMA;
MYE_ff_next <= MYE_ff;
MCnt_next <= MCnt;
MActive_next <= MActive;
case vicCycle is
when cycleRefresh4 =>
-- 7. In the first phase of cycle 15, it is checked if the expansion flip flop
-- is set. If so, MCBASE is incremented by 2.
for i in 0 to 7 loop
if MDMA(i) and MYE_ff(i) = '1' then
MCBase_next(i) <= MCBase(i) + 2;
end if;
end loop;
when cycleRefresh5 =>
-- 8. In the first phase of cycle 16, it is checked if the expansion flip flop
-- is set. If so, MCBASE is incremented by 1. After that, the VIC checks if
-- MCBASE is equal to 63 and turns of the DMA and the display of the sprite if it is.
for i in 0 to 7 loop
if MDMA(i) then
if MYE_ff(i) = '1' then
MCBase_next(i) <= MCBase(i) + 1;
if MCBase(i) = 62 then
MDMA_next(i) <= false;
MActive_next(i) <= false;
end if;
else
if MYE(i) = '0' then
-- this is from debugging Robocop fixed cart intro
MCBase_next(i) <= MCBase(i) - 1;
elsif MCBASE(i) = 63 then
MDMA_next(i) <= false;
MActive_next(i) <= false;
end if;
end if;
end if;
end loop;
when cycleCalcSprites =>
-- 2. If the MxYE bit is set in the first phase of cycle 55, the expansion
-- flip flop is inverted.
for i in 0 to 7 loop
if MYE(i) = '1' then
MYE_ff_next(i) <= not MYE_ff(i);
end if;
end loop;
-- 3. In the first phases of cycle 55 and 56, the VIC checks for every sprite
-- if the corresponding MxE bit in register $d015 is set and the Y
-- coordinate of the sprite (odd registers $d001-$d00f) match the lower 8
-- bits of RASTER. If this is the case and the DMA for the sprite is still
-- off, the DMA is switched on, MCBASE is cleared, and if the MxYE bit is
-- set the expansion flip flip is reset.
for i in 0 to 7 loop
if not MDMA(i) and ME(i) = '1' and rasterY(7 downto 0) = MY(i) then
MCBase_Next(i) <= (others => '0');
MDMA_Next(i) <= true;
if MYE(i) = '1' then
MYE_ff_Next(i) <= '0';
end if;
end if;
end loop;
when cycleSpriteA =>
-- 4. In the first phase of cycle 58, the MC of every sprite is loaded from
-- its belonging MCBASE (MCBASE->MC) and it is checked if the DMA for the
-- sprite is turned on and the Y coordinate of the sprite matches the lower
-- 8 bits of RASTER. If this is the case, the display of the sprite is
-- turned on.
if sprite = "000" then
for i in 0 to 7 loop
MCnt_Next(i) <= MCBase(i);
if MDMA(i) and ME(i) = '1' and rasterY(7 downto 0) = MY(i) then
MActive_Next(i) <= true;
end if;
end loop;
end if;
when others => null;
end case;
-- 1. The expansion flip flip is set as long as the bit in MxYE in register
-- $d017 corresponding to the sprite is cleared.
for i in 0 to 7 loop
if MYE(i) = '0' then
MYE_ff_next(i) <= '1';
end if;
end loop;
end process;
process(clk)
begin
if rising_edge(clk) then
if phi = '0'
and enaData = '1' then
case vicCycle is
when cycleRefresh5 =>
for i in 0 to 7 loop
MYE_ff(i) <= not MYE_ff(i);
if MActive(i) then
if MYE_ff(i) = MYE(i) then
MCnt(i) <= MCnt(i) + 1;
else
MCnt(i) <= MCnt(i) - 2;
end if;
end if;
end loop;
when others =>
null;
end case;
MCBase <= MCBase_Next;
MDMA <= MDMA_Next;
MYE_ff <= MYE_ff_Next;
MCnt <= MCnt_Next;
MActive <= MActive_Next;
end if;
for i in 0 to 7 loop
if MYE(i) = '0'
or not MActive(i) then
MYE_ff(i) <= '0';
end if;
end loop;
--
-- On cycleCalcSprite check for each inactive sprite if
-- there is a Y match. Reset MCnt if this is so.
--
-- The RasterX counter is used here to multiplex the compare logic.
-- This saves a few logic cells in the FPGA.
if vicCycle = cycleCalcSprites then
if (not MActive(to_integer(RasterX(2 downto 0))))
and (ME(to_integer(RasterX(2 downto 0))) = '1')
and (rasterY(7 downto 0) = MY(to_integer(RasterX(2 downto 0)))) then
MCnt(to_integer(RasterX(2 downto 0))) <= (others => '0');
end if;
end if;
--
-- Original non-multiplexed version
-- if vicCycle = cycleCalcSprites then
-- for i in 0 to 7 loop
-- if (not MActive(i))
-- and (ME(i) = '1')
-- and (rasterY(7 downto 0) = MY(i)) then
-- MCnt(i) <= (others => '0');
-- end if;
-- end loop;
-- end if;
--
-- Increment MCnt after fetching data.
-- 5. If the DMA for a sprite is turned on, three s-accesses are done in
-- sequence in the corresponding cycles assigned to the sprite (see the
-- diagrams in section 3.6.3.). The p-accesses are always done, even if the
-- sprite is turned off. The read data of the first access is stored in the
-- upper 8 bits of the shift register, that of the second one in the middle
-- 8 bits and that of the third one in the lower 8 bits.
-- MC is incremented by one after each s-access.
if enaData = '1' then
if (vicCycle = cycleSpriteA and phi = '1')
or (vicCycle = cycleSpriteB and phi = '0') then
if MActive(to_integer(sprite)) then
if MDMA(to_integer(sprite)) then
MCnt(to_integer(sprite)) <= MCnt(to_integer(sprite)) + 1;
end if;
end if;
@@ -1064,7 +1119,7 @@ calcBitmap: process(clk)
MShift(to_integer(sprite)) <= false;
end if;
if Mactive(to_integer(sprite)) then
if Mactive_Next(to_integer(sprite)) then
if phi = '0' then
case vicCycle is
when cycleSpriteB =>