vga/ps/2: ip-core hinzugefuegt

[hwmod.git] / src / textmode_vga / video_memory_beh.vhd

diff --git a/src/textmode_vga/video_memory_beh.vhd b/src/textmode_vga/video_memory_beh.vhd
new file mode 100644 (file)
index 0000000..094026d
--- /dev/null
+++ b/src/textmode_vga/video_memory_beh.vhd
@@ -0,0 +1,52 @@
+-------------------------------------------------------------------------\r
+--\r
+-- Filename: video_memory_beh.vhd\r
+-- =========\r
+--\r
+-- Short Description:\r
+-- ==================\r
+--   Behavioral implementation of the video memory. The access time\r
+--   is exactly one clock cycle.\r
+--\r
+-------------------------------------------------------------------------\r
+\r
+library ieee;
+use ieee.std_logic_1164.all;
+use ieee.numeric_std.all;
+use work.textmode_vga_pkg.all;
+use work.font_pkg.all;
+
+architecture beh of video_memory is
+  subtype RAM_ENTRY is std_logic_vector(DATA_WIDTH - 1 downto 0);
+  type RAM_TYPE is array(0 to (2 ** (ROW_ADDR_WIDTH + COL_ADDR_WIDTH)) - 1) of RAM_ENTRY;
+  signal ram : RAM_TYPE :=
+  (
+    others => (others => '0')
+  ); 
+begin
+  process(vga_clk)
+    variable vga_row_address_int, sm_row_address_int : integer range 0 to 2 * LINE_COUNT - 2;
+    variable vga_row_address_vector, sm_row_address_vector : std_logic_vector(ROW_ADDR_WIDTH - 1 downto 0);
+    variable vga_address, sm_address : std_logic_vector(COL_ADDR_WIDTH + ROW_ADDR_WIDTH - 1 downto 0);
+  begin
+    if rising_edge(vga_clk) then
+      vga_row_address_int := to_integer(unsigned(vga_row_address)) + to_integer(unsigned(sm_scroll_address));
+      if vga_row_address_int > LINE_COUNT - 1 then
+        vga_row_address_int := vga_row_address_int - LINE_COUNT;
+      end if;
+      vga_row_address_vector := std_logic_vector(to_unsigned(vga_row_address_int, ROW_ADDR_WIDTH));
+      vga_address := vga_row_address_vector & vga_col_address;
+      vga_data <= ram(to_integer(unsigned(vga_address)));
+      
+      if sm_wr = '1' then
+        sm_row_address_int := to_integer(unsigned(sm_row_address)) + to_integer(unsigned(sm_scroll_address));
+        if sm_row_address_int > LINE_COUNT - 1 then
+          sm_row_address_int := sm_row_address_int - LINE_COUNT;
+        end if;
+        sm_row_address_vector := std_logic_vector(to_unsigned(sm_row_address_int, ROW_ADDR_WIDTH));
+        sm_address := sm_row_address_vector & sm_col_address;
+        ram(to_integer(unsigned(sm_address))) <= sm_data;
+      end if;
+    end if;
+  end process;
+end architecture beh;