Subversion Repositories pmodsf3driver

------------------------------------------------------------------------

-- Engineer:    Dalmasso Loic

-- Create Date: 19/02/2025

-- Module Name: PmodSF3SPIFrequencyGenerator

-- Description:

--      Pmod SF3 SPI Frequency Generator for the 32 MB NOR Flash Memory MT25QL256ABA.

--              From the System Input Clock, this module generate valid SPI Serial Clock Frequency according to the actual Dummy Cycles and SPI Mode (Single, Dual, Quad).

--              If the wanted SPI Serial Clock Frequency cannot be generated (i.e., Specified SPI Flash Frequency > System Input Clock Frequency), the System Input Clock Frequency is used.

--              When the System Input Clock Frequency is used, the 'o_using_sys_freq' signal is set.

--

--              SPI Frequency References (in MHz):

--              | Dummy Cycles | Single SPI | Dual SPI | Quad SPI |

--              |          0       |    133     |        94    |   133    |

--              |          1       |     94     |        79    |        44    |

--              |          2       |    112     |        97    |        61    |

--              |          3       |    129     |       106    |        78    |

--              |          4       |    133     |       115    |        97    |

--              |          5       |    133     |       125    |   106    |

--              |          6       |    133     |       133    |   115    |

--              |          7       |    133     |        94    |   125    |

--              |          8       |    133     |        94    |   133    |

--              |          9       |    133     |        94    |   133    |

--              |          10      |    133     |        94    |   133    |

--              |          11      |    133     |        94    |   133    |

--              |          12      |    133     |        94    |   133    |

--              |          13      |    133     |        94    |   133    |

--              |          14      |    133     |        94    |   133    |

--

-- Generics

--              sys_clock: System Input Clock Frequency (Hz)

--

-- Ports

--              Input   -       i_sys_clock: System Input Clock

--              Input   -       i_reset: System Input Reset ('0': No Reset, '1': Reset)

--              Input   -       i_spi_single_enable: Enable SPI Single Mode ('0': Disable, '1': Enable)

--              Input   -       i_spi_dual_enable: Enable SPI Dual Mode ('0': Disable, '1': Enable)

--              Input   -       i_dummy_cycles: Number of Dummy Cycles (0 to 14 cycles)

--              Output  -       o_spi_freq: SPI Serial Clock Frequency

--              Output  -       o_using_sys_freq: System Input Clock as SPI Serial Clock Frequency ('0': Disable, '1': Enable)

------------------------------------------------------------------------

LIBRARY IEEE;

USE IEEE.STD_LOGIC_1164.ALL;

USE IEEE.NUMERIC_STD.ALL;

USE IEEE.MATH_REAL.ALL;

ENTITY PmodSF3SPIFrequencyGenerator is

GENERIC(

    sys_clock: INTEGER := 100_000_000

);

PORT(

        i_sys_clock: IN STD_LOGIC;

        i_reset: IN STD_LOGIC;

        i_spi_single_enable: IN STD_LOGIC;

        i_spi_dual_enable: IN STD_LOGIC;

        i_dummy_cycles: IN INTEGER range 0 to 15;

        o_spi_freq: OUT STD_LOGIC;

        o_using_sys_freq: OUT STD_LOGIC

);

END PmodSF3SPIFrequencyGenerator;

ARCHITECTURE Behavioral of PmodSF3SPIFrequencyGenerator is

------------------------------------------------------------------------

-- Constant Declarations

------------------------------------------------------------------------

-- ROM Type

type ROM_TYPE is array(INTEGER range 0 to 14) of INTEGER;

-- No SPI Frequency Divider (use System Input Clock Frequency)

constant NO_SPI_DIVIDER: INTEGER := 0;

-- SPI Mode Frequency ROM Initialization

function spi_mode_rom_initialization (rom_ref: ROM_TYPE) return ROM_TYPE is

variable spi_freq: INTEGER;

variable spi_freq_rom: ROM_TYPE;

begin

        for index in INTEGER range 0 to 14 loop

                -- Get SPI Single Mode Frequency from ROM Reference (in MHz)

                spi_freq := rom_ref(index) * 1_000_000;

                -- Compare System Clock to ROM Reference

                if (spi_freq > sys_clock) then

                        -- No Clock Divider

                        spi_freq_rom(index) := NO_SPI_DIVIDER;

                else

                        -- Clock Divider

                        spi_freq_rom(index) := INTEGER((real(sys_clock) / real(spi_freq))) -1;

                end if;

        end loop;

        return spi_freq_rom;

end spi_mode_rom_initialization;

-- ROM Memories (Frequency Inputs in MHz)

constant SINGLE_SPI_ROM: rom_type := spi_mode_rom_initialization(rom_ref => (133, 94, 112, 129, 133, 133, 133, 133, 133, 133, 133, 133, 133, 133, 133));

constant DUAL_SPI_ROM: rom_type := spi_mode_rom_initialization(rom_ref => (94, 79, 97, 106, 115, 125, 133, 94, 94, 94, 94, 94, 94, 94, 94));

constant QUAD_SPI_ROM: rom_type := spi_mode_rom_initialization(rom_ref => (133, 44, 61, 78, 97, 106, 115, 125, 133, 133, 133, 133, 133, 133, 133));

------------------------------------------------------------------------

-- Signal Declarations

------------------------------------------------------------------------

-- SPI Clock Divider Reference

signal spi_clock_div_ref: INTEGER := 0;

-- SPI Clock Divider

signal spi_clock_div: INTEGER := 0;

-- SPI Serial Clock Frequency Register

signal spi_freq_reg: STD_LOGIC := '0';

------------------------------------------------------------------------

-- Module Implementation

------------------------------------------------------------------------

begin

        ------------------------

        -- SPI Clock Dividers --

        ------------------------

        process(i_sys_clock)

        begin

                if rising_edge(i_sys_clock) then

                        -- SPI Single Mode

                        if (i_spi_single_enable = '1') then

                                spi_clock_div_ref <= SINGLE_SPI_ROM(i_dummy_cycles);

                        -- SPI Dual Mode

                        elsif (i_spi_dual_enable = '1') then

                                spi_clock_div_ref <= DUAL_SPI_ROM(i_dummy_cycles);

                        -- SPI Quad Mode

                        else

                                spi_clock_div_ref <= QUAD_SPI_ROM(i_dummy_cycles);

                        end if;

                end if;

        end process;

        -----------------------

        -- SPI Clock Counter --

        -----------------------

        process(i_sys_clock)

        begin

                if rising_edge(i_sys_clock) then

                        -- Reset SPI Clock Divider

                        if (i_reset = '1') or (spi_clock_div = 0) then

                                spi_clock_div <= spi_clock_div_ref;

                        -- Decrement SPI Clock Divider

                        else

                                spi_clock_div <= spi_clock_div -1;

                        end if;

                end if;

        end process;

        --------------------------------

        -- SPI Serial Clock Frequency --

        --------------------------------

        process(i_sys_clock)

        begin

                if rising_edge(i_sys_clock) then

                        -- Reset Frequency Register

                        if (i_reset = '1') then

                                spi_freq_reg <= '0';

                        -- Set Frequency Register

                        elsif (spi_clock_div = 0) then

                                spi_freq_reg <= '1';

                        else

                                spi_freq_reg <= '0';

                        end if;

                end if;

        end process;

        o_spi_freq <= spi_freq_reg;

        ------------------------------------------------------

        -- System Input Clock as SPI Serial Clock Frequency --

        ------------------------------------------------------

        process(i_sys_clock)

        begin

                if rising_edge(i_sys_clock) then

                        -- SPI Clock Enable

                        if (spi_clock_div_ref = NO_SPI_DIVIDER) then

                                o_using_sys_freq <= '1';

                        else

                                o_using_sys_freq <= '0';

                        end if;

                end if;

        end process;

end Behavioral;