genrams/generic_shiftreg_fifo: force native SRL implementation on Xilinx devices

Conflicts:

	modules/genrams/xilinx/Manifest.py

modules/genrams/generic_shiftreg_fifo.vhd

@@ -72,13 +72,20 @@ end generic_shiftreg_fifo;
 
 architecture rtl of generic_shiftreg_fifo is
 
-  constant c_srl_length : integer := g_size;  -- set to srl 'type' 16 or 32 bit length
-
-  type t_srl_array is array (c_srl_length - 1 downto 0) of std_logic_vector (g_data_width - 1 downto 0);
-
-  signal fifo_store : t_srl_array;
-  signal pointer    : integer range 0 to c_srl_length - 1;
+  component gc_shiftreg
+    generic (
+      g_size : integer);
+    port (
+      clk_i : in  std_logic;
+      en_i  : in  std_logic;
+      d_i   : in  std_logic;
+      q_o   : out std_logic;
+      a_i   : in  std_logic_vector(f_log2_size(g_size)-1 downto 0));
+  end component;
+  
+  signal pointer    : integer range 0 to g_size-1;
 
+  signal srl_addr : std_logic_vector(f_log2_size(g_size)-1 downto 0);
   signal pointer_zero        : std_logic;
   signal pointer_full        : std_logic;
   signal pointer_almost_full : std_logic;
@@ -92,22 +99,21 @@ begin
   do_write <= '1' when (rd_i = '1' and we_i = '1')
               or (we_i = '1' and pointer_full = '0') else '0';
 
--- data store SRL's
-  p_data_srl : process(clk_i)
-  begin
-    if rising_edge(clk_i) then
---      if rst_n_i = '0'then
---        for i in 0 to c_srl_length-1 loop
---          fifo_store(i) <= (others => '0');
---        end loop;  -- i
-      if do_write = '1' then
-        fifo_store <= fifo_store(fifo_store'left - 1 downto 0) & d_i;
-      end if;
-    end if;
-  end process;
 
-  q_o <= fifo_store(pointer);
+  gen_sregs: for i in 0 to g_data_width-1 generate
+    U_SRLx: gc_shiftreg
+      generic map (
+        g_size => g_size)
+      port map (
+        clk_i => clk_i,
+        en_i  => do_write,
+        d_i   => d_i(i),
+        q_o   => q_o(i),
+        a_i   => srl_addr);
+  end generate gen_sregs;
 
+  srl_addr <= std_logic_vector(to_unsigned(pointer, srl_addr'length));
+  
   p_empty_logic : process(clk_i)
   begin
     if rising_edge(clk_i) then
@@ -149,8 +155,8 @@ begin
 
   -- Detect when pointer is zero and maximum
   pointer_zero        <= '1' when pointer = 0                                      else '0';
-  pointer_full        <= '1' when pointer = c_srl_length - 1                       else '0';
-  pointer_almost_full <= '1' when pointer_full = '1' or pointer = c_srl_length - 2 else '0';
+  pointer_full        <= '1' when pointer = g_size - 1                       else '0';
+  pointer_almost_full <= '1' when pointer_full = '1' or pointer = g_size - 2 else '0';
 
 
   -- assign internal signals to outputs

modules/genrams/xilinx/Manifest.py

@@ -3,4 +3,6 @@ files = [
 "generic_dpram_sameclock.vhd",
 "generic_dpram_dualclock.vhd",
 "generic_simple_dpram.vhd",
-"generic_spram.vhd"];
+"generic_spram.vhd",
+"gc_shiftreg.vhd"]
+

modules/genrams/xilinx/gc_shiftreg.vhd

+library ieee;
+
+use ieee.STD_LOGIC_1164.all;
+use ieee.NUMERIC_STD.all;
+
+use work.genram_pkg.all;
+
+entity gc_shiftreg is
+  
+  generic (
+    g_size : integer);
+
+  port (
+    clk_i : in  std_logic;
+    en_i  : in  std_logic;
+    d_i   : in  std_logic;
+    q_o   : out std_logic;
+    a_i   : in  std_logic_vector(f_log2_size(g_size)-1 downto 0));
+
+end gc_shiftreg;
+
+
+architecture wrapper of gc_shiftreg is
+
+  component SRLC32E
+    port (
+      Q   : out std_ulogic;
+      A   : in  std_logic_vector (4 downto 0);
+      CE  : in  std_ulogic;
+      CLK : in  std_ulogic;
+      D   : in  std_ulogic);
+  end component;
+
+  signal a  : std_logic_vector(4 downto 0);
+  signal sr : std_logic_vector(g_size-1 downto 0);
+  
+begin  -- wrapper
+
+  assert (g_size <= 32) report "gc_shiftreg[xilinx]: forced SRL32 implementation can be done only for 32-bit or smaller shift registers" severity warning;
+
+  a <= std_logic_vector(resize(unsigned(a_i), 5));
+
+  gen_srl32 : if(g_size <= 32) generate
+    U_SRLC32 : SRLC32E
+      port map (
+        Q   => q_o,
+        A   => a,
+        CE  => en_i,
+        CLK => clk_i,
+        D   => d_i);
+  end generate gen_srl32;
+
+  gen_inferred : if(g_size > 32) generate
+
+    p_srl : process(clk_i)
+    begin
+      if rising_edge(clk_i) then
+        if en_i = '1' then
+          sr <= sr(sr'left - 1 downto 0) & d_i;
+        end if;
+      end if;
+    end process;
+
+    q_o <= sr(TO_INTEGER(unsigned(a_i)));
+  end generate gen_inferred;
+  
+
+end wrapper;