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neorv32/rtl/core/neorv32_spi.vhd

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-- #################################################################################################
-- # << NEORV32 - Serial Peripheral Interface Controller (SPI) >> #
-- # ********************************************************************************************* #
-- # BSD 3-Clause License #
-- # #
-- # The NEORV32 RISC-V Processor, https://github.com/stnolting/neorv32 #
-- # Copyright (c) 2024, Stephan Nolting. All rights reserved. #
-- # #
-- # Redistribution and use in source and binary forms, with or without modification, are #
-- # permitted provided that the following conditions are met: #
-- # #
-- # 1. Redistributions of source code must retain the above copyright notice, this list of #
-- # conditions and the following disclaimer. #
-- # #
-- # 2. Redistributions in binary form must reproduce the above copyright notice, this list of #
-- # conditions and the following disclaimer in the documentation and/or other materials #
-- # provided with the distribution. #
-- # #
-- # 3. Neither the name of the copyright holder nor the names of its contributors may be used to #
-- # endorse or promote products derived from this software without specific prior written #
-- # permission. #
-- # #
-- # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS #
-- # OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF #
-- # MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE #
-- # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, #
-- # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE #
-- # GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED #
-- # AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING #
-- # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED #
-- # OF THE POSSIBILITY OF SUCH DAMAGE. #
-- #################################################################################################
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
library neorv32;
use neorv32.neorv32_package.all;
entity neorv32_spi is
generic (
IO_SPI_FIFO : natural range 1 to 2**15 -- SPI RTX fifo depth, has to be a power of two, min 1
);
port (
clk_i : in std_ulogic; -- global clock line
rstn_i : in std_ulogic; -- global reset line, low-active, async
bus_req_i : in bus_req_t; -- bus request
bus_rsp_o : out bus_rsp_t; -- bus response
clkgen_en_o : out std_ulogic; -- enable clock generator
clkgen_i : in std_ulogic_vector(07 downto 0);
spi_clk_o : out std_ulogic; -- SPI serial clock
spi_dat_o : out std_ulogic; -- controller data out, peripheral data in
spi_dat_i : in std_ulogic; -- controller data in, peripheral data out
spi_csn_o : out std_ulogic_vector(07 downto 0); -- SPI CS
irq_o : out std_ulogic -- transmission done interrupt
);
end neorv32_spi;
architecture neorv32_spi_rtl of neorv32_spi is
-- control register --
constant ctrl_en_c : natural := 0; -- r/w: spi enable
constant ctrl_cpha_c : natural := 1; -- r/w: spi clock phase
constant ctrl_cpol_c : natural := 2; -- r/w: spi clock polarity
constant ctrl_cs_sel0_c : natural := 3; -- r/w: spi CS select bit 0
constant ctrl_cs_sel1_c : natural := 4; -- r/w: spi CS select bit 1
constant ctrl_cs_sel2_c : natural := 5; -- r/w: spi CS select bit 2
constant ctrl_cs_en_c : natural := 6; -- r/w: enable selected cs line (set bit -> clear line)
constant ctrl_prsc0_c : natural := 7; -- r/w: spi prescaler select bit 0
constant ctrl_prsc1_c : natural := 8; -- r/w: spi prescaler select bit 1
constant ctrl_prsc2_c : natural := 9; -- r/w: spi prescaler select bit 2
constant ctrl_cdiv0_c : natural := 10; -- r/w: clock divider bit 0
constant ctrl_cdiv1_c : natural := 11; -- r/w: clock divider bit 1
constant ctrl_cdiv2_c : natural := 12; -- r/w: clock divider bit 2
constant ctrl_cdiv3_c : natural := 13; -- r/w: clock divider bit 3
constant ctrl_highspeed_c : natural := 14; -- r/w: high-speed mode
--
constant ctrl_rx_avail_c : natural := 16; -- r/-: rx fifo data available (fifo not empty)
constant ctrl_tx_empty_c : natural := 17; -- r/-: tx fifo empty
constant ctrl_tx_nhalf_c : natural := 18; -- r/-: tx fifo not at least half full
constant ctrl_tx_full_c : natural := 19; -- r/-: tx fifo full
constant ctrl_irq_rx_avail_c : natural := 20; -- r/w: fire irq if rx fifo data available (fifo not empty)
constant ctrl_irq_tx_empty_c : natural := 21; -- r/w: fire irq if tx fifo empty
constant ctrl_irq_tx_nhalf_c : natural := 22; -- r/w: fire irq if tx fifo not at least half full
constant ctrl_fifo_size0_c : natural := 23; -- r/-: log2(fifo size), bit 0 (lsb)
constant ctrl_fifo_size1_c : natural := 24; -- r/-: log2(fifo size), bit 1
constant ctrl_fifo_size2_c : natural := 25; -- r/-: log2(fifo size), bit 2
constant ctrl_fifo_size3_c : natural := 26; -- r/-: log2(fifo size), bit 3 (msb)
--
constant ctrl_busy_c : natural := 31; -- r/-: spi phy busy or tx fifo not empty yet
-- control register --
type ctrl_t is record
enable : std_ulogic;
cpha : std_ulogic;
cpol : std_ulogic;
cs_sel : std_ulogic_vector(2 downto 0);
cs_en : std_ulogic;
prsc : std_ulogic_vector(2 downto 0);
cdiv : std_ulogic_vector(3 downto 0);
highspeed : std_ulogic;
irq_rx_avail : std_ulogic;
irq_tx_empty : std_ulogic;
irq_tx_nhalf : std_ulogic;
end record;
signal ctrl : ctrl_t;
-- clock generator --
signal cdiv_cnt : std_ulogic_vector(3 downto 0);
signal spi_clk_en : std_ulogic;
-- spi transceiver --
type rtx_engine_t is record
state : std_ulogic_vector(2 downto 0);
busy : std_ulogic;
sreg : std_ulogic_vector(7 downto 0);
bitcnt : std_ulogic_vector(3 downto 0);
sdi_sync : std_ulogic;
sck : std_ulogic;
done : std_ulogic;
end record;
signal rtx_engine : rtx_engine_t;
-- FIFO interface --
type fifo_t is record
we : std_ulogic; -- write enable
re : std_ulogic; -- read enable
clear : std_ulogic; -- sync reset, high-active
wdata : std_ulogic_vector(7 downto 0); -- write data
rdata : std_ulogic_vector(7 downto 0); -- read data
avail : std_ulogic; -- data available?
free : std_ulogic; -- free entry available?
half : std_ulogic; -- half full
end record;
signal tx_fifo, rx_fifo : fifo_t;
begin
-- Bus Access -----------------------------------------------------------------------------
-- -------------------------------------------------------------------------------------------
bus_access: process(rstn_i, clk_i)
begin
if (rstn_i = '0') then
bus_rsp_o.ack <= '0';
bus_rsp_o.err <= '0';
bus_rsp_o.data <= (others => '0');
ctrl.enable <= '0';
ctrl.cpha <= '0';
ctrl.cpol <= '0';
ctrl.cs_sel <= (others => '0');
ctrl.cs_en <= '0';
ctrl.prsc <= (others => '0');
ctrl.cdiv <= (others => '0');
ctrl.highspeed <= '0';
ctrl.irq_rx_avail <= '0';
ctrl.irq_tx_empty <= '0';
ctrl.irq_tx_nhalf <= '0';
elsif rising_edge(clk_i) then
-- bus handshake --
bus_rsp_o.ack <= bus_req_i.stb;
bus_rsp_o.err <= '0';
bus_rsp_o.data <= (others => '0');
if (bus_req_i.stb = '1') then
-- write access --
if (bus_req_i.rw = '1') then
if (bus_req_i.addr(2) = '0') then -- control register
ctrl.enable <= bus_req_i.data(ctrl_en_c);
ctrl.cpha <= bus_req_i.data(ctrl_cpha_c);
ctrl.cpol <= bus_req_i.data(ctrl_cpol_c);
ctrl.cs_sel <= bus_req_i.data(ctrl_cs_sel2_c downto ctrl_cs_sel0_c);
ctrl.cs_en <= bus_req_i.data(ctrl_cs_en_c);
ctrl.prsc <= bus_req_i.data(ctrl_prsc2_c downto ctrl_prsc0_c);
ctrl.cdiv <= bus_req_i.data(ctrl_cdiv3_c downto ctrl_cdiv0_c);
ctrl.highspeed <= bus_req_i.data(ctrl_highspeed_c);
ctrl.irq_rx_avail <= bus_req_i.data(ctrl_irq_rx_avail_c);
ctrl.irq_tx_empty <= bus_req_i.data(ctrl_irq_tx_empty_c);
ctrl.irq_tx_nhalf <= bus_req_i.data(ctrl_irq_tx_nhalf_c);
end if;
-- read access --
else
if (bus_req_i.addr(2) = '0') then -- control register
bus_rsp_o.data(ctrl_en_c) <= ctrl.enable;
bus_rsp_o.data(ctrl_cpha_c) <= ctrl.cpha;
bus_rsp_o.data(ctrl_cpol_c) <= ctrl.cpol;
bus_rsp_o.data(ctrl_cs_sel2_c downto ctrl_cs_sel0_c) <= ctrl.cs_sel;
bus_rsp_o.data(ctrl_cs_en_c) <= ctrl.cs_en;
bus_rsp_o.data(ctrl_prsc2_c downto ctrl_prsc0_c) <= ctrl.prsc;
bus_rsp_o.data(ctrl_cdiv3_c downto ctrl_cdiv0_c) <= ctrl.cdiv;
bus_rsp_o.data(ctrl_highspeed_c) <= ctrl.highspeed;
--
bus_rsp_o.data(ctrl_rx_avail_c) <= rx_fifo.avail;
bus_rsp_o.data(ctrl_tx_empty_c) <= not tx_fifo.avail;
bus_rsp_o.data(ctrl_tx_nhalf_c) <= not tx_fifo.half;
bus_rsp_o.data(ctrl_tx_full_c) <= not tx_fifo.free;
bus_rsp_o.data(ctrl_irq_rx_avail_c) <= ctrl.irq_rx_avail;
bus_rsp_o.data(ctrl_irq_tx_empty_c) <= ctrl.irq_tx_empty;
bus_rsp_o.data(ctrl_irq_tx_nhalf_c) <= ctrl.irq_tx_nhalf;
--
bus_rsp_o.data(ctrl_fifo_size3_c downto ctrl_fifo_size0_c) <= std_ulogic_vector(to_unsigned(index_size_f(IO_SPI_FIFO), 4));
--
bus_rsp_o.data(ctrl_busy_c) <= rtx_engine.busy or tx_fifo.avail;
else
bus_rsp_o.data(7 downto 0) <= rx_fifo.rdata;
end if;
end if;
end if;
end if;
end process bus_access;
-- direct chip-select (low-active) --
chip_select: process(rstn_i, clk_i)
begin
if (rstn_i = '0') then
spi_csn_o <= (others => '1');
elsif rising_edge(clk_i) then
spi_csn_o <= (others => '1'); -- default: all disabled
if (ctrl.cs_en = '1') and (ctrl.enable = '1') then
spi_csn_o(to_integer(unsigned(ctrl.cs_sel))) <= '0';
end if;
end if;
end process chip_select;
-- Data FIFO ("Ring Buffer") --------------------------------------------------------------
-- -------------------------------------------------------------------------------------------
-- TX FIFO --
tx_fifo_inst: entity neorv32.neorv32_fifo
generic map (
FIFO_DEPTH => IO_SPI_FIFO, -- number of fifo entries; has to be a power of two; min 1
FIFO_WIDTH => 8, -- size of data elements in fifo
FIFO_RSYNC => true, -- sync read
FIFO_SAFE => true, -- safe access
FULL_RESET => false -- no HW reset, try to infer BRAM
)
port map (
-- control --
clk_i => clk_i, -- clock, rising edge
rstn_i => rstn_i, -- async reset, low-active
clear_i => tx_fifo.clear, -- sync reset, high-active
half_o => tx_fifo.half, -- FIFO at least half-full
-- write port --
wdata_i => tx_fifo.wdata, -- write data
we_i => tx_fifo.we, -- write enable
free_o => tx_fifo.free, -- at least one entry is free when set
-- read port --
re_i => tx_fifo.re, -- read enable
rdata_o => tx_fifo.rdata, -- read data
avail_o => tx_fifo.avail -- data available when set
);
tx_fifo.clear <= not ctrl.enable;
tx_fifo.we <= '1' when (bus_req_i.stb = '1') and (bus_req_i.rw = '1') and (bus_req_i.addr(2) = '1') else '0';
tx_fifo.wdata <= bus_req_i.data(7 downto 0);
tx_fifo.re <= '1' when (rtx_engine.state = "100") else '0';
-- RX FIFO --
rx_fifo_inst: entity neorv32.neorv32_fifo
generic map (
FIFO_DEPTH => IO_SPI_FIFO, -- number of fifo entries; has to be a power of two; min 1
FIFO_WIDTH => 8, -- size of data elements in fifo
FIFO_RSYNC => true, -- sync read
FIFO_SAFE => true, -- safe access
FULL_RESET => false -- no HW reset, try to infer BRAM
)
port map (
-- control --
clk_i => clk_i, -- clock, rising edge
rstn_i => rstn_i, -- async reset, low-active
clear_i => rx_fifo.clear, -- sync reset, high-active
half_o => rx_fifo.half, -- FIFO at least half-full
-- write port --
wdata_i => rx_fifo.wdata, -- write data
we_i => rx_fifo.we, -- write enable
free_o => rx_fifo.free, -- at least one entry is free when set
-- read port --
re_i => rx_fifo.re, -- read enable
rdata_o => rx_fifo.rdata, -- read data
avail_o => rx_fifo.avail -- data available when set
);
rx_fifo.clear <= not ctrl.enable;
rx_fifo.wdata <= rtx_engine.sreg;
rx_fifo.we <= rtx_engine.done;
rx_fifo.re <= '1' when (bus_req_i.stb = '1') and (bus_req_i.rw = '0') and (bus_req_i.addr(2) = '1') else '0';
-- IRQ generator --
irq_generator: process(rstn_i, clk_i)
begin
if (rstn_i = '0') then
irq_o <= '0';
elsif rising_edge(clk_i) then
irq_o <= ctrl.enable and (
(ctrl.irq_rx_avail and rx_fifo.avail) or -- IRQ if RX FIFO is not empty
(ctrl.irq_tx_empty and (not tx_fifo.avail)) or -- IRQ if TX FIFO is empty
(ctrl.irq_tx_nhalf and (not tx_fifo.half))); -- IRQ if TX buffer is not half full
end if;
end process irq_generator;
-- SPI Transceiver ------------------------------------------------------------------------
-- -------------------------------------------------------------------------------------------
transceiver: process(rstn_i, clk_i)
begin
if (rstn_i = '0') then
rtx_engine.done <= '0';
rtx_engine.state <= (others => '0');
rtx_engine.bitcnt <= (others => '0');
rtx_engine.sreg <= (others => '0');
rtx_engine.sdi_sync <= '0';
rtx_engine.sck <= '0';
elsif rising_edge(clk_i) then
-- defaults --
rtx_engine.done <= '0';
-- serial engine --
rtx_engine.state(2) <= ctrl.enable;
case rtx_engine.state is
when "100" => -- enabled but idle, waiting for new transmission trigger
-- ------------------------------------------------------------
rtx_engine.sck <= ctrl.cpol;
rtx_engine.bitcnt <= (others => '0');
if (tx_fifo.avail = '1') then -- trigger new transmission
rtx_engine.sreg <= tx_fifo.rdata;
rtx_engine.state(1 downto 0) <= "01";
end if;
when "101" => -- start with next new clock pulse
-- ------------------------------------------------------------
if (spi_clk_en = '1') then
if (ctrl.cpha = '1') then -- clock phase shift
rtx_engine.sck <= not ctrl.cpol;
end if;
rtx_engine.state(1 downto 0) <= "10";
end if;
when "110" => -- first phase of bit transmission
-- ------------------------------------------------------------
if (spi_clk_en = '1') then
rtx_engine.sck <= not (ctrl.cpha xor ctrl.cpol);
rtx_engine.sdi_sync <= spi_dat_i; -- sample data input
rtx_engine.bitcnt <= std_ulogic_vector(unsigned(rtx_engine.bitcnt) + 1);
rtx_engine.state(1 downto 0) <= "11";
end if;
when "111" => -- second phase of bit transmission
-- ------------------------------------------------------------
if (spi_clk_en = '1') then
rtx_engine.sreg <= rtx_engine.sreg(6 downto 0) & rtx_engine.sdi_sync; -- shift and set output
if (rtx_engine.bitcnt(3) = '1') then -- all bits transferred?
rtx_engine.sck <= ctrl.cpol;
rtx_engine.done <= '1'; -- done!
rtx_engine.state(1 downto 0) <= "00"; -- transmission done
else
rtx_engine.sck <= ctrl.cpha xor ctrl.cpol;
rtx_engine.state(1 downto 0) <= "10";
end if;
end if;
when others => -- "0--": SPI deactivated
-- ------------------------------------------------------------
rtx_engine.sck <= ctrl.cpol;
rtx_engine.state(1 downto 0) <= "00";
end case;
end if;
end process transceiver;
-- PHY busy flag --
rtx_engine.busy <= '0' when (rtx_engine.state(1 downto 0) = "00") else '1';
-- SPI output --
spi_dat_o <= rtx_engine.sreg(7); -- MSB first
spi_clk_o <= rtx_engine.sck;
-- SPI Clock Generator --------------------------------------------------------------------
-- -------------------------------------------------------------------------------------------
clock_generator: process(rstn_i, clk_i)
begin
if (rstn_i = '0') then
spi_clk_en <= '0';
cdiv_cnt <= (others => '0');
elsif rising_edge(clk_i) then
spi_clk_en <= '0'; -- default
if (ctrl.enable = '0') then -- reset/disabled
cdiv_cnt <= (others => '0');
elsif (clkgen_i(to_integer(unsigned(ctrl.prsc))) = '1') or (ctrl.highspeed = '1') then -- pre-scaled clock
if (cdiv_cnt = ctrl.cdiv) then -- clock divider for fine-tuning
spi_clk_en <= '1';
cdiv_cnt <= (others => '0');
else
cdiv_cnt <= std_ulogic_vector(unsigned(cdiv_cnt) + 1);
end if;
end if;
end if;
end process clock_generator;
-- clock generator enable --
clkgen_en_o <= ctrl.enable;
end neorv32_spi_rtl;
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