From 417fadf2f6eee1cfe6d1c39c4ce36194000c38b2 Mon Sep 17 00:00:00 2001
From: Tomasz Wlostowski <tomasz.wlostowski@cern.ch>
Date: Tue, 12 Jul 2011 16:29:45 +0200
Subject: [PATCH] xwb_bus_fanout: initial upload

---
 modules/wishbone/wb_bus_fanout/Manifest.py    |   1 +
 .../wishbone/wb_bus_fanout/xwb_bus_fanout.vhd | 128 ++++++++++++++++++
 2 files changed, 129 insertions(+)
 create mode 100644 modules/wishbone/wb_bus_fanout/Manifest.py
 create mode 100644 modules/wishbone/wb_bus_fanout/xwb_bus_fanout.vhd

diff --git a/modules/wishbone/wb_bus_fanout/Manifest.py b/modules/wishbone/wb_bus_fanout/Manifest.py
new file mode 100644
index 00000000..52a36cd8
--- /dev/null
+++ b/modules/wishbone/wb_bus_fanout/Manifest.py
@@ -0,0 +1 @@
+files = ["xwb_bus_fanout.vhd" ];
diff --git a/modules/wishbone/wb_bus_fanout/xwb_bus_fanout.vhd b/modules/wishbone/wb_bus_fanout/xwb_bus_fanout.vhd
new file mode 100644
index 00000000..71facd60
--- /dev/null
+++ b/modules/wishbone/wb_bus_fanout/xwb_bus_fanout.vhd
@@ -0,0 +1,128 @@
+library ieee;
+use ieee.STD_LOGIC_1164.all;
+use ieee.numeric_std.all;
+
+use work.wishbone_pkg.all;
+
+entity xwb_bus_fanout is
+  
+  generic (
+    g_num_outputs    : natural;
+    g_bits_per_slave : integer := 14);
+
+  port (
+    clk_sys_i : in std_logic;
+    rst_n_i   : in std_logic;
+
+    slave_i : in t_wishbone_slave_in;
+    slave_o : out t_wishbone_slave_out;
+
+    master_i : in t_wishbone_master_in_array(0 to g_num_outputs-1);
+    master_o : out t_wishbone_master_out_array(0 to g_num_outputs-1)
+    );
+
+end xwb_bus_fanout;
+
+architecture rtl of xwb_bus_fanout is
+
+  constant c_periph_addr_bits : integer := 3;
+  
+  signal periph_addr     : std_logic_vector(c_periph_addr_bits - 1 downto 0);
+  signal periph_addr_reg : std_logic_vector(c_periph_addr_bits - 1 downto 0);
+
+  signal periph_sel     : std_logic_vector(g_num_outputs - 1 downto 0);
+  signal periph_sel_reg : std_logic_vector(g_num_outputs - 1 downto 0);
+
+  signal ack_muxed     : std_logic;
+  signal data_in_muxed : std_logic_vector(31 downto 0);
+
+  signal cycle_in_progress : std_logic;
+  signal ack_prev : std_logic;
+  
+begin  -- rtl
+
+  periph_addr <= slave_i.adr(g_bits_per_slave+c_periph_addr_bits-1 downto g_bits_per_slave);
+
+  onehot_decode : process (periph_addr)  -- periph_sel <= onehot_decode(periph_addr)
+    variable temp1 : std_logic_vector (periph_sel'high downto 0);
+    variable temp2 : integer range 0 to periph_sel'high;
+  begin
+    temp1 := (others => '0');
+    temp2 := 0;
+    for i in periph_addr'range loop
+      if (periph_addr(i) = '1') then
+        temp2 := 2*temp2+1;
+      else
+        temp2 := 2*temp2;
+      end if;
+    end loop;
+    temp1(temp2) := '1';
+    periph_sel   <= temp1;
+  end process;
+
+
+  ACK_MUX : process (periph_addr_reg, master_i)
+  begin
+    if(to_integer(unsigned(periph_addr_reg)) < g_num_outputs) then
+      ack_muxed <= master_i(to_integer(unsigned(periph_addr_reg))).ack;
+    else
+      ack_muxed <= '0';
+    end if;
+  end process;
+
+
+  DIN_MUX : process (periph_addr_reg, master_i)
+  begin
+    if(to_integer(unsigned(periph_addr_reg))) < g_num_outputs then
+      data_in_muxed <= master_i(to_integer(unsigned(periph_addr_reg))).dat;
+    else
+      data_in_muxed <= (others => 'X');
+    end if;
+  end process;
+
+
+  p_arbitrate : process(clk_sys_i)
+  begin
+    if rising_edge(clk_sys_i) then
+      if rst_n_i = '0' then
+        slave_o.ack       <= '0';
+        cycle_in_progress <= '0';
+        ack_prev <= '0';
+        periph_addr_reg <= (others => '0');
+        periph_sel_reg <= (others => '0');
+      else
+        periph_sel_reg  <= periph_sel;
+        periph_addr_reg <= periph_addr;
+
+        if(cycle_in_progress = '0') then
+          if(slave_i.cyc = '1') then
+            cycle_in_progress <= '1';
+          end if;
+          ack_prev <= '0';
+        else
+          slave_o.dat <= data_in_muxed;
+          slave_o.ack <= ack_muxed;
+          ack_prev <= ack_muxed;
+          if(ack_muxed = '1') then
+            cycle_in_progress <= '0';
+          end if;
+        end if;
+      end if;
+    end if;
+  end process;
+
+  gen_outputs : for i in 0 to g_num_outputs-1 generate
+    master_o(i).cyc <= slave_i.cyc and periph_sel(i);
+    master_o(i).adr <= slave_i.adr;
+    master_o(i).dat <= slave_i.dat;
+    master_o(i).stb <= slave_i.stb and not (not cycle_in_progress and ack_prev);
+    master_o(i).we  <= slave_i.we;
+    master_o(i).sel <= slave_i.sel;
+  end generate gen_outputs;
+
+
+  slave_o.err   <= '0';
+  slave_o.stall <= '0';
+  slave_o.rty   <= '0';
+  
+end rtl;
-- 
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