diff options
Diffstat (limited to 'basys3/basys3.srcs/ppu_addr_dec.vhd')
| -rw-r--r-- | basys3/basys3.srcs/ppu_addr_dec.vhd | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/basys3/basys3.srcs/ppu_addr_dec.vhd b/basys3/basys3.srcs/ppu_addr_dec.vhd index 33f247c..649d582 100644 --- a/basys3/basys3.srcs/ppu_addr_dec.vhd +++ b/basys3/basys3.srcs/ppu_addr_dec.vhd @@ -20,7 +20,7 @@ entity ppu_addr_dec is port( -- address decoder end ppu_addr_dec; architecture Behavioral of ppu_addr_dec is - signal TMM_RANGE, BAM_RANGE, FAM_RANGE, PAL_RANGE, AUX_RANGE : std_logic := '0'; -- ADDR in range of memory area + signal NUL_RANGE, TMM_RANGE, BAM_RANGE, FAM_RANGE, PAL_RANGE, AUX_RANGE : std_logic := '0'; -- ADDR in range of memory area begin -- address MUX TMM_ADDR <= ADDR(PPU_TMM_ADDR_WIDTH-1 downto 0); @@ -29,12 +29,13 @@ begin PAL_ADDR <= ADDR(PPU_PAL_ADDR_WIDTH-1 downto 0); AUX_ADDR <= ADDR(PPU_AUX_ADDR_WIDTH-1 downto 0); + NUL_RANGE <= '1' when (and ADDR) else '0'; -- address is 0xffff -- WEN MUX - TMM_WEN <= TMM_RANGE and WEN; - BAM_WEN <= BAM_RANGE and WEN; - FAM_WEN <= FAM_RANGE and WEN; - PAL_WEN <= PAL_RANGE and WEN; - AUX_WEN <= AUX_RANGE and WEN; + TMM_WEN <= TMM_RANGE and WEN and (not NUL_RANGE); + BAM_WEN <= BAM_RANGE and WEN and (not NUL_RANGE); + FAM_WEN <= FAM_RANGE and WEN and (not NUL_RANGE); + PAL_WEN <= PAL_RANGE and WEN and (not NUL_RANGE); + AUX_WEN <= AUX_RANGE and WEN and (not NUL_RANGE); -- address ranges TMM_RANGE <= '1' when not ((ADDR(15) and ADDR(14) and ADDR(13)) or (ADDR(15) and ADDR(14) and ADDR(12))) else '0'; |