diff options
Diffstat (limited to 'basys3/basys3.srcs/ppu_consts.vhd')
| -rw-r--r-- | basys3/basys3.srcs/ppu_consts.vhd | 23 |
1 files changed, 20 insertions, 3 deletions
diff --git a/basys3/basys3.srcs/ppu_consts.vhd b/basys3/basys3.srcs/ppu_consts.vhd index 722954d..75b6168 100644 --- a/basys3/basys3.srcs/ppu_consts.vhd +++ b/basys3/basys3.srcs/ppu_consts.vhd @@ -1,12 +1,18 @@ +library ieee; +use ieee.math_real.all; + -- https://docs.google.com/spreadsheets/d/1MU6K4c4PtMR_JXIpc3I0ZJdLZNnoFO7G2P3olCz6LSc package ppu_consts is + -- utility functions + function ceil_log2(n : natural) return natural; + constant PPU_RAM_BUS_ADDR_WIDTH : natural := 16; -- RAM bus address width constant PPU_RAM_BUS_DATA_WIDTH : natural := 16; -- RAM bus data width constant PPU_FG_SPRITE_COUNT : natural := 128; -- foreground sprites constant PPU_COLOR_OUTPUT_DEPTH : natural := 4; -- VGA output channel depth constant PPU_PALETTE_COLOR_WIDTH : natural := 3; -- palette index width (within sprite) constant PPU_PALETTE_INDEX_WIDTH : natural := 3; -- palette index width (palette table) - constant PPU_PALETTE_CIDX_WIDTH : natural := PPU_PALETTE_COLOR_WIDTH + PPU_PALETTE_INDEX_WIDTH; -- global palette index width + constant PPU_PALETTE_CIDX_WIDTH : natural := (PPU_PALETTE_COLOR_WIDTH + PPU_PALETTE_INDEX_WIDTH); -- global palette index width constant PPU_TMM_ADDR_WIDTH : natural := 16; -- tilemap memory ram bus address width constant PPU_TMM_DATA_WIDTH : natural := 15; -- tilemap memory ram bus data width constant PPU_BAM_ADDR_WIDTH : natural := 11; -- background attribute memory ram bus address width @@ -32,7 +38,18 @@ package ppu_consts is constant PPU_BG_CANVAS_TILE_V_WIDTH : natural := 5; -- bits needed to describe vertical bg tile index (grid coordinates) constant PPU_TILE_INDEX_WIDTH : natural := 10; -- bits needed to index a tile from TMM memory constant PPU_PIXELS_PER_TILE_WORD : natural := 5; -- pixels defined in one word in TMM memory - constant PPU_SPRITE_PIXELS_PER_WORD : natural := 52; -- words needed for a single sprite + constant PPU_SPRITE_WORD_COUNT : natural := 52; -- words needed for a single sprite constant PPU_PIXEL_BIT_WIDTH : natural := 3; -- bits needed to identify pixel in TMM word + constant PPU_TILE_BIT_WIDTH : natural := (PPU_SPRITE_WIDTH * PPU_SPRITE_HEIGHT * PPU_PALETTE_COLOR_WIDTH); -- bits in single tile + constant PPU_TMM_CACHE_FETCH_C_COUNT : natural := PPU_SPRITE_WORD_COUNT + 1; + constant PPU_TMM_CACHE_FETCH_A_COUNT : natural := PPU_TMM_CACHE_FETCH_C_COUNT * PPU_FG_SPRITE_COUNT; -- amount of clocks to fetch new TMM cache + constant PPU_TMM_CACHE_FETCH_A_WIDTH : natural := ceil_log2(PPU_TMM_CACHE_FETCH_A_COUNT); end package ppu_consts; - +package body ppu_consts is + -- https://stackoverflow.com/questions/21783280/number-of-bits-to-represent-an-integer-in-vhdl + -- Returns number of bits required to represent val in binary vector + function ceil_log2(n : natural) return natural is + begin + return natural(integer(ceil(log2(real(n - 1))))); + end function; +end package body ppu_consts; |