ram/rom garbage data eliminated.

diff --git a/de1_nes/mem/prg_rom.vhd b/de1_nes/mem/prg_rom.vhd
index 234903d..90e524f 100644 (file)
--- a/de1_nes/mem/prg_rom.vhd
+++ b/de1_nes/mem/prg_rom.vhd
@@ -73,17 +73,22 @@ signal p_rom : rom_array := rom_fill;
 --attribute ram_init_file : string;
 --attribute ram_init_file of p_rom : signal is "sample1-prg.hex";
 
+signal wk_data  : std_logic_vector (dbus_size - 1 downto 0);
+
 begin
 
     p : process (clk)
     begin
     if (rising_edge(clk)) then
         if (ce_n = '0') then
-            data <= p_rom(conv_integer(addr));
+            wk_data <= p_rom(conv_integer(addr));
         else
-            data <= (others => 'Z');
+            wk_data <= (others => 'Z');
         end if;
     end if;
     end process;
+    
+    data <= wk_data when ce_n = '0' else
+            (others => 'Z');
 end rtl;
 

diff --git a/de1_nes/mem/ram.vhd b/de1_nes/mem/ram.vhd
index d51d843..bcc1289 100644 (file)
--- a/de1_nes/mem/ram.vhd
+++ b/de1_nes/mem/ram.vhd
@@ -26,6 +26,8 @@ signal work_ram : ram_array := (others => (others => '0'));
 constant RAM_TAOE : time := 25 ns;      --OE access time
 constant RAM_TOH : time := 10 ns;       --write data hold time
 
+signal wk_d_io    : std_logic_vector (dbus_size - 1 downto 0);
+
 begin
     p_write : process (clk)
     begin
@@ -40,12 +42,15 @@ begin
     begin
     if (rising_edge(clk)) then
         if (ce_n= '0' and we_n = '1' and oe_n = '0') then
-            d_io <= work_ram(conv_integer(addr));
+            wk_d_io <= work_ram(conv_integer(addr));
         else
-            d_io <= (others => 'Z');
+            wk_d_io <= (others => 'Z');
         end if;
     end if;
     end process;
+    
+    d_io <= wk_d_io when ce_n= '0' and we_n = '1' and oe_n = '0' else
+            (others => 'Z');
 end rtl;
 
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