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spi_adc.vhd

   1  -- spi_adc.vhd : SPI Decoder
   2  -- Copyright (C) 2006 Brno University of Technology,
   3  --                    Faculty of Information Technology
   4  -- Author(s): Zdenek Vasicek <xvasic11 AT stud.fit.vutbr.cz>
   5  --
   6  -- LICENSE TERMS
   7  --
   8  -- Redistribution and use in source and binary forms, with or without
   9  -- modification, are permitted provided that the following conditions
  10  -- are met:
  11  -- 1. Redistributions of source code must retain the above copyright
  12  --    notice, this list of conditions and the following disclaimer.
  13  -- 2. Redistributions in binary form must reproduce the above copyright
  14  --    notice, this list of conditions and the following disclaimer in
  15  --    the documentation and/or other materials provided with the
  16  --    distribution.
  17  -- 3. All advertising materials mentioning features or use of this software
  18  --    or firmware must display the following acknowledgement:
  19  --
  20  --      This product includes software developed by the University of
  21  --      Technology, Faculty of Information Technology, Brno and its
  22  --      contributors.
  23  --
  24  -- 4. Neither the name of the Company nor the names of its contributors
  25  --    may be used to endorse or promote products derived from this
  26  --    software without specific prior written permission.
  27  --
  28  -- This software or firmware is provided ``as is'', and any express or implied
  29  -- warranties, including, but not limited to, the implied warranties of
  30  -- merchantability and fitness for a particular purpose are disclaimed.
  31  -- In no event shall the company or contributors be liable for any
  32  -- direct, indirect, incidental, special, exemplary, or consequential
  33  -- damages (including, but not limited to, procurement of substitute
  34  -- goods or services; loss of use, data, or profits; or business
  35  -- interruption) however caused and on any theory of liability, whether
  36  -- in contract, strict liability, or tort (including negligence or
  37  -- otherwise) arising in any way out of the use of this software, even
  38  -- if advised of the possibility of such damage.
  39  --
  40  -- $Id$
  41  --
  42  --
  43  
  44  library ieee;
  45  use ieee.std_logic_1164.all;
  46  use ieee.std_logic_arith.all;
  47  use ieee.std_logic_unsigned.all;
  48  use work.math_pack.all;
  49  
  50  -- SYNTH-ISE: slices=28, slicesFF=36, 4luts=47
  51  architecture basic of SPI_adc is
  52  
  53  subtype tcntr is integer range 0 to max(ADDR_WIDTH, DATA_WIDTH);
  54  signal  bitcntr : tcntr := 0;
  55  signal  bitcntr_rst : std_logic;
  56  
  57  signal  cmp_4bits : std_logic;
  58  signal  cmp_baseaddr : std_logic;
  59  signal  cmp_abits : std_logic;
  60  signal  cmp_dbits : std_logic;
  61  signal  cmp_bitszero : std_logic;
  62  
  63  type    FSMstate is (SCmdRcv, SAddrRcv, SDataRcv, SNop);
  64  signal  pstate    : FSMstate; -- actual state
  65  signal  nstate    : FSMstate; -- next state
  66  
  67  signal  shreg_cmd  : std_logic_vector(1 downto 0);
  68  signal  cmdreg_en  : std_logic;
  69  alias   cmd_we     : std_logic is shreg_cmd(0);
  70  alias   cmd_re     : std_logic is shreg_cmd(1);
  71  signal  shreg_addr : std_logic_vector(ADDR_WIDTH-1 downto 0);
  72  signal  addrreg_en : std_logic;
  73  signal  shreg_do   : std_logic_vector(DATA_WIDTH-1 downto 0);
  74  signal  shreg_di   : std_logic_vector(DATA_WIDTH-1 downto 0);
  75  signal  shreg_ld   : std_logic;
  76  signal  doreg_en   : std_logic;
  77  signal  rden       : std_logic;
  78  signal  diouten    : std_logic;
  79  signal  rden_reg   : std_logic_vector(max(DELAY,0) downto 0);
  80  
  81  begin
  82  
  83     DATA_OUT <= shreg_do;
  84     ADDR <= shreg_addr(max(ADDR_OUT_WIDTH-1,0) DOWNTO 0);
  85     READ_EN <= rden;
  86  
  87     -- DI MX
  88     DI <= shreg_di(DATA_WIDTH-1) when (diouten='1') else 'Z';
  89  
  90     -- Bits counter
  91     bitecntr: process(CS, CLK)
  92     begin
  93        if (CS = '0') then
  94           bitcntr <= 0;
  95        elsif (CLK'event) and (CLK='1') then
  96           if (bitcntr_rst = '1') then
  97              bitcntr <= 0;
  98           elsif (DO_VLD='1') then
  99              bitcntr <= bitcntr + 1;
 100           end if;
 101        end if;
 102     end process;
 103  
 104     -- Comparators
 105     cmp_4bits <= '1' when (bitcntr = 4) else '0';
 106     cmp_abits <= '1' when (bitcntr = ADDR_WIDTH) else '0';
 107     cmp_dbits <= '1' when (bitcntr = DATA_WIDTH) else '0';
 108     cmp_bitszero <= '1' when (bitcntr = 0) else '0';
 109  
 110     cmp_baseaddr <= '1' when (shreg_addr(ADDR_WIDTH-1 downto ADDR_OUT_WIDTH) =
 111                               conv_std_logic_vector(BASE_ADDR,ADDR_WIDTH)(ADDR_WIDTH-1 downto ADDR_OUT_WIDTH))
 112                         else '0';
 113  
 114     -- ShReg Load delay
 115     shreg_ld <= rden_reg(DELAY);
 116     rden_reg(0) <= rden;
 117     process (CS, CLK)
 118     begin
 119        if (DELAY > 0) then
 120           if (CS = '0') then
 121              rden_reg(DELAY downto 1) <= (others=>'0');
 122           elsif (CLK'event) and (CLK='1') then
 123              rden_reg(DELAY downto 1) <= rden_reg(DELAY-1 downto 0);
 124           end if;
 125        end if;
 126     end process;
 127  
 128     -- Address register
 129     process (CS, CLK)
 130     begin
 131        if (CS = '0') then
 132           shreg_addr <= (others=>'0');
 133        elsif (CLK'event) and (CLK = '1') then
 134           if (DO_VLD='1') and (addrreg_en='1') then -- Shift enable
 135              shreg_addr <= shreg_addr(ADDR_WIDTH-2 downto 0) & DO;
 136           end if;
 137        end if;
 138     end process;
 139  
 140     -- Shift registers
 141     process (CS, CLK)
 142     begin
 143        if (CS = '0') then
 144           shreg_cmd <= (others=>'0');
 145           shreg_do  <= (others=>'0');
 146           shreg_di  <= (others=>'0');
 147        elsif (CLK'event) and (CLK='1') then
 148  
 149           if (DO_VLD='1') then -- shift enable
 150              if (cmdreg_en='1') then  -- CMD register
 151                 shreg_cmd <= shreg_cmd(0) & DO;
 152              end if;
 153              if (doreg_en='1') then   -- DATA register
 154                 shreg_do <= shreg_do(DATA_WIDTH-2 downto 0) & DO;
 155              end if;
 156           end if;
 157  
 158           if (shreg_ld='1') then  -- parallel load
 159              shreg_di <= DATA_IN;
 160           elsif (DI_REQ='1') then -- shift enable
 161              shreg_di <= shreg_di(DATA_WIDTH-2 downto 0)&'0';
 162           end if;
 163        end if;
 164     end process;
 165  
 166     -- FSM
 167     process (CS, CLK)
 168     begin
 169        if (CS = '0') then
 170           pstate <= SCmdRcv;
 171        elsif (CLK'event) and (CLK='1') then
 172           pstate <= nstate;
 173        end if;
 174     end process;
 175  
 176     -- FSM next state logic
 177     process (pstate, cmp_4bits, cmp_abits, cmp_dbits, cmp_bitszero, cmp_baseaddr, shreg_cmd, cmd_we, cmd_re, DI_REQ)
 178     begin
 179        bitcntr_rst <= '0';
 180        cmdreg_en <= '0';
 181        doreg_en <= '0';
 182        addrreg_en <= '0';
 183        WRITE_EN <= '0';
 184        rden <= '0';
 185        diouten <= '0';
 186  
 187        nstate <= SCmdRcv;
 188        case pstate is
 189           --CMD receive
 190           when SCmdRcv =>
 191              cmdreg_en <= '1';
 192              if (cmp_4bits = '1') then
 193                 nstate <= SAddrRcv;
 194                 bitcntr_rst <= '1';
 195              end if;
 196  
 197           --ADDR receive
 198           when SAddrRcv =>
 199              nstate <= SAddrRcv;
 200              addrreg_en <= '1';
 201              if (cmp_abits = '1') then
 202                 if (cmp_baseaddr = '1') then
 203                    nstate <= SDataRcv;
 204                 else
 205                    nstate <= SNop;
 206                 end if;
 207                 bitcntr_rst <= '1';
 208              end if;
 209  
 210           --DATA receive & transmitt
 211           when SDataRcv =>
 212              nstate <= SDataRcv;
 213              doreg_en <= '1';
 214              diouten <= '1';
 215              if (cmp_bitszero = '1') and (DI_REQ = '1') then
 216                 rden <= cmd_re;
 217              end if;
 218              if (cmp_dbits = '1') then
 219                 WRITE_EN <= cmd_we;
 220                 bitcntr_rst <= '1';
 221              end if;
 222  
 223            --inactive device (different BASE_ADDR)
 224            when SNop =>
 225              nstate <= SNop;
 226              bitcntr_rst <= '1';
 227  
 228       end case;
 229     end process;
 230  
 231  
 232  end basic;
 233