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    /spi_master_slave/trunk/rtl
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Rev 13 → Rev 12

/grp_debouncer.vhd File deleted
/spi_slave.vhd
115,10 → 115,6
-- Removed global signal setting at the FSM, implementing exhaustive explicit signal attributions
-- for each state, to avoid reported inference problems in some synthesis engines.
-- Streamlined port names and indentation blocks.
-- 2011/08/01 v2.01.0115 [JD] Adjusted 'do_valid_o' pulse width to be 2 'clk_i', as in the master core.
-- Simulated in iSim with the master core for continuous transmission mode.
-- 2011/08/02 v2.02.0120 [JD] Added mux for MISO at reset state, to output di(N-1) at start. This fixed a bug in first bit.
-- The master and slave cores were verified in FPGA with continuous transmission, for all SPI modes.
--
--
-----------------------------------------------------------------------------------------------------------------------
125,11 → 121,12
-- TODO
-- ====
--
--
-----------------------------------------------------------------------------------------------------------------------
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use ieee.std_logic_unsigned.all;
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
 
entity spi_slave is
Generic (
153,7 → 150,7
do_transfer_o : out std_logic; -- debug: internal transfer driver
wren_o : out std_logic; -- debug: internal state of the wren_i pulse stretcher
rx_bit_next_o : out std_logic; -- debug: internal rx bit
state_dbg_o : out std_logic_vector (3 downto 0); -- debug: internal state register
state_dbg_o : out std_logic_vector (5 downto 0); -- debug: internal state register
sh_reg_dbg_o : out std_logic_vector (N-1 downto 0) -- debug: internal shift register
);
end spi_slave;
168,7 → 165,7
-- synthesis tool will remove the receive logic from the generated circuitry.
--================================================================================================================
 
architecture rtl of spi_slave is
architecture RTL of spi_slave is
-- constants to control FlipFlop synthesis
constant SHIFT_EDGE : std_logic := (CPOL xnor CPHA); -- MOSI data is captured and shifted at this SCK edge
constant CHANGE_EDGE : std_logic := (CPOL xor CPHA); -- MISO data is updated at this SCK edge
183,25 → 180,25
-- By using GSR for the initialization, and reducing RESET local init to the bare
-- essential, the model achieves better LUT/FF packing and CLB usability.
------------------------------------------------------------------------------------------
-- internal state signals for register and combinatorial stages
-- internal state signals for register and combinational stages
signal state_next : natural range N downto 0 := 0; -- state 0 is idle state
signal state_reg : natural range N downto 0 := 0; -- state 0 is idle state
-- shifter signals for register and combinatorial stages
signal sh_next : std_logic_vector (N-1 downto 0);
signal sh_reg : std_logic_vector (N-1 downto 0);
-- shifter signals for register and combinational stages
signal sh_next : std_logic_vector (N-1 downto 0) := (others => '0');
signal sh_reg : std_logic_vector (N-1 downto 0) := (others => '0');
-- mosi and miso connections
signal rx_bit_next : std_logic;
signal tx_bit_next : std_logic;
signal tx_bit_reg : std_logic;
-- buffered di_i data signals for register and combinatorial stages
signal rx_bit_next : std_logic := '0';
signal tx_bit_next : std_logic := '0';
signal tx_bit_reg : std_logic := '0';
-- buffered di_i data signals for register and combinational stages
signal di_reg : std_logic_vector (N-1 downto 0);
-- internal wren_i stretcher for fsm combinatorial stage
-- internal wren_i stretcher for fsm combinational stage
signal wren : std_logic;
signal wr_ack_next : std_logic := '0';
signal wr_ack_reg : std_logic := '0';
-- buffered do_o data signals for register and combinatorial stages
signal do_buffer_next : std_logic_vector (N-1 downto 0);
signal do_buffer_reg : std_logic_vector (N-1 downto 0);
-- buffered do_o data signals for register and combinational stages
signal do_buffer_next : std_logic_vector (N-1 downto 0) := (others => '0');
signal do_buffer_reg : std_logic_vector (N-1 downto 0) := (others => '0');
-- internal signal to flag transfer to do_buffer_reg
signal do_transfer_next : std_logic := '0';
signal do_transfer_reg : std_logic := '0';
294,7 → 291,7
end process in_transfer_proc;
 
--=============================================================================================
-- REGISTER TRANSFER PROCESSES
-- RTL CORE REGISTER PROCESSES
--=============================================================================================
-- fsm state and data registers change on spi SHIFT_EDGE
core_reg_proc : process (spi_sck_i, spi_ssel_i) is
320,9 → 317,9
end process core_reg_proc;
 
--=============================================================================================
-- COMBINATORIAL LOGIC PROCESSES
-- RTL COMBINATIONAL LOGIC PROCESSES
--=============================================================================================
-- state and datapath combinatorial logic
-- state and datapath combinational logic
core_combi_proc : process ( sh_reg, sh_next, state_reg, tx_bit_reg, rx_bit_next, do_buffer_reg,
do_transfer_reg, di_reg, di_req_reg, wren, wr_ack_reg) is
begin
335,16 → 332,15
di_req_next <= di_req_reg; -- data input request
state_next <= state_reg; -- fsm control state
case state_reg is
when (N) =>
-- stretch do_valid
wr_ack_next <= '0'; -- acknowledge data in transfer
-- acknowledge write enable
wr_ack_next <= '1'; -- acknowledge data in transfer
do_transfer_next <= '0'; -- reset transfer signal
di_req_next <= '0'; -- prefetch data request: deassert when shifting data
tx_bit_next <= sh_reg(N-1); -- output next MSbit
sh_next(N-1 downto 1) <= sh_reg(N-2 downto 0); -- shift inner bits
sh_next(0) <= rx_bit_next; -- shift in rx bit into LSb
state_next <= state_reg - 1; -- update next state at each sck pulse
when (N-1) downto (PREFETCH+3) =>
-- send bit out and shif bit in
do_transfer_next <= '0'; -- reset transfer signal
354,7 → 350,6
sh_next(N-1 downto 1) <= sh_reg(N-2 downto 0); -- shift inner bits
sh_next(0) <= rx_bit_next; -- shift in rx bit into LSb
state_next <= state_reg - 1; -- update next state at each sck pulse
when (PREFETCH+2) downto 3 =>
-- raise data prefetch request
di_req_next <= '1'; -- request data in advance to allow for pipeline delays
363,7 → 358,6
sh_next(N-1 downto 1) <= sh_reg(N-2 downto 0); -- shift inner bits
sh_next(0) <= rx_bit_next; -- shift in rx bit into LSb
state_next <= state_reg - 1; -- update next state at each sck pulse
when 2 =>
-- transfer parallel data on next state
di_req_next <= '1'; -- request data in advance to allow for pipeline delays
374,7 → 368,6
do_transfer_next <= '1'; -- signal transfer to do_buffer on next cycle
do_buffer_next <= sh_next; -- get next data directly into rx buffer
state_next <= state_reg - 1; -- update next state at each sck pulse
when 1 =>
-- restart from state 'N' if more sck pulses come
sh_next(0) <= rx_bit_next; -- shift in rx bit into LSb
381,6 → 374,7
sh_next(N-1 downto 1) <= di_reg(N-2 downto 0); -- shift inner bits
tx_bit_next <= di_reg(N-1); -- first output bit comes from the MSb of parallel data
di_req_next <= '0'; -- prefetch data request: deassert when shifting data
do_transfer_next <= '0'; -- clear signal transfer to do_buffer
if wren = '1' then -- load tx register if valid data present at di_reg
wr_ack_next <= '1'; -- acknowledge data in transfer
state_next <= N; -- next state is top bit of new data
389,53 → 383,44
sh_next <= (others => '0'); -- load null data (output '0' if no load)
state_next <= 0; -- next state is idle state
end if;
when 0 =>
sh_next(0) <= rx_bit_next; -- shift in rx bit into LSb
sh_next(N-1 downto 1) <= di_reg(N-2 downto 0); -- shift inner bits
wr_ack_next <= '1'; -- acknowledge data in transfer
di_req_next <= '0'; -- prefetch data request: deassert when shifting data
-- idle state: start and end of transmission
if CPHA = '1' then
wr_ack_next <= '1'; -- acknowledge data in transfer
di_req_next <= '0'; -- prefetch data request: deassert when shifting data
sh_next(0) <= rx_bit_next; -- shift in rx bit into LSb
sh_next(N-1 downto 1) <= di_reg(N-2 downto 0); -- shift inner bits
else
wr_ack_next <= '1'; -- acknowledge data in transfer
di_req_next <= not wr_ack_reg; -- will request data if shifter empty
sh_next <= di_reg; -- load parallel data from di_reg into shifter
end if;
do_transfer_next <= '0'; -- clear signal transfer to do_buffer
tx_bit_next <= di_reg(N-1); -- first output bit comes from the MSb of parallel data
state_next <= N; -- next state is top bit of new data
when others =>
state_next <= 0; -- safe state
end case;
end process core_combi_proc;
 
--=============================================================================================
-- OUTPUT LOGIC PROCESSES
-- RTL OUTPUT LOGIC PROCESSES
--=============================================================================================
-- data output processes
spi_miso_o_proc: spi_miso_o <= tx_bit_reg; -- connect MISO driver
do_o_proc : do_o <= do_buffer_reg; -- do_o always available
do_valid_o_proc: do_valid_o <= do_valid_o_reg; -- copy registered do_valid_o to output
di_req_o_proc: di_req_o <= di_req_o_reg; -- copy registered di_req_o to output
wr_ack_o_proc: wr_ack_o <= wr_ack_reg; -- copy registered wr_ack_o to output
 
-----------------------------------------------------------------------------------------------
-- MISO driver process: copy next tx bit at reset
-----------------------------------------------------------------------------------------------
-- this is a MUX that selects the combinatorial next tx bit at reset, and the registered tx bit
-- at sequential operation. The mux gives us a preload of the first bit, simplifying the shifter logic.
spi_miso_o_proc: process (spi_ssel_i, tx_bit_reg, tx_bit_next) is
begin
if spi_ssel_i = '1' then
spi_miso_o <= tx_bit_next; -- copy next => reg at reset
else
spi_miso_o <= tx_bit_reg;
end if;
end process spi_miso_o_proc;
 
--=============================================================================================
-- DEBUG LOGIC PROCESSES
--=============================================================================================
-- these signals are useful for verification, and can be deleted after debug.
-- these signals are useful for verification, and can be deleted or commented-out after debug.
do_transfer_proc: do_transfer_o <= do_transfer_reg;
state_debug_proc: state_dbg_o <= std_logic_vector(to_unsigned(state_reg, 4)); -- export internal state to debug
state_debug_proc: state_dbg_o <= std_logic_vector(to_unsigned(state_reg, 6)); -- export internal state to debug
rx_bit_next_proc: rx_bit_next_o <= rx_bit_next;
wren_o_proc: wren_o <= wren;
sh_reg_debug_proc: sh_reg_dbg_o <= sh_reg; -- export sh_reg to debug
end architecture rtl;
end architecture RTL;
 
/spi_master.vhd
13,7 → 13,6
-- a frequency that is 2x the spi SCK line frequency. The divider value is passed as a generic parameter during instantiation.
-- All parallel i/o interface operations are synchronous to the 'pclk_i' high speed clock, that can be asynchronous to the serial
-- 'sclk_i' clock.
-- For optimized use of longlines, connect 'sclk_i' and 'pclk_i' to the same global clock line.
-- Fully pipelined cross-clock circuitry guarantees that no setup artifacts occur on the buffers that are accessed by the two
-- clock domains.
-- The block is very simple to use, and has parallel inputs and outputs that behave like a synchronous memory i/o.
144,8 → 143,6
-- 2011/07/29 v1.14.0130 [JD] Removed global signal setting at the FSM, implementing exhaustive explicit signal attributions
-- for each state, to avoid reported inference problems in some synthesis engines.
-- Streamlined port names and indentation blocks.
-- 2011/08/01 v1.15.0135 [JD] Fixed latch inference for spi_mosi_o driver at the fsm.
-- The master and slave cores were verified in FPGA with continuous transmission, for all SPI modes.
--
-----------------------------------------------------------------------------------------------------------------------
-- TODO
196,7 → 193,7
do_transfer_o : out std_logic; -- debug: internal transfer driver
wren_o : out std_logic; -- debug: internal state of the wren_i pulse stretcher
rx_bit_reg_o : out std_logic; -- debug: internal rx bit
state_dbg_o : out std_logic_vector (3 downto 0); -- debug: internal state register
state_dbg_o : out std_logic_vector (5 downto 0); -- debug: internal state register
core_clk_o : out std_logic;
core_n_clk_o : out std_logic;
core_ce_o : out std_logic;
209,7 → 206,7
-- this architecture is a pipelined register-transfer description.
-- all signals are clocked at the rising edge of the system clock 'sclk_i'.
--================================================================================================================
architecture rtl of spi_master is
architecture RTL of spi_master is
-- core clocks, generated from 'sclk_i': initialized to differential values
signal core_clk : std_logic := '0'; -- continuous core clock, positive logic
signal core_n_clk : std_logic := '1'; -- continuous core clock, negative logic
237,14 → 234,14
signal state_next : natural range N+1 downto 0 := 0;
signal state_reg : natural range N+1 downto 0 := 0;
-- shifter signals for register and combinatorial stages
signal sh_next : std_logic_vector (N-1 downto 0);
signal sh_reg : std_logic_vector (N-1 downto 0);
signal sh_next : std_logic_vector (N-1 downto 0) := (others => '0');
signal sh_reg : std_logic_vector (N-1 downto 0) := (others => '0');
-- input bit sampled buffer
signal rx_bit_reg : std_logic := '0';
-- buffered di_i data signals for register and combinatorial stages
signal di_reg : std_logic_vector (N-1 downto 0);
signal di_reg : std_logic_vector (N-1 downto 0) := (others => '0');
-- internal wren_i stretcher for fsm combinatorial stage
signal wren : std_logic;
signal wren : std_logic := '0';
signal wr_ack_next : std_logic := '0';
signal wr_ack_reg : std_logic := '0';
-- internal SSEL enable control signals
254,8 → 251,8
signal sck_ena_next : std_logic;
signal sck_ena_reg : std_logic;
-- buffered do_o data signals for register and combinatorial stages
signal do_buffer_next : std_logic_vector (N-1 downto 0);
signal do_buffer_reg : std_logic_vector (N-1 downto 0);
signal do_buffer_next : std_logic_vector (N-1 downto 0) := (others => '0');
signal do_buffer_reg : std_logic_vector (N-1 downto 0) := (others => '0');
-- internal signal to flag transfer to do_buffer_reg
signal do_transfer_next : std_logic := '0';
signal do_transfer_reg : std_logic := '0';
312,7 → 309,7
-- The clock enable phase is selected for serial input sampling, fsm clocking, and spi SCK output,
-- based on the configuration of CPOL and CPHA.
-- Each phase is selected so that all the registers can be clocked with a rising edge on all SPI
-- modes, by a single high-speed global clock, preserving clock resources and clock to data skew.
-- modes, by a single high-speed global clock, preserving clock resources.
-----------------------------------------------------------------------------------------------
-- generate the 2x spi base clock enable from the serial high-speed input clock
spi_2x_ce_gen_proc: process (sclk_i) is
360,6 → 357,7
begin
spi_clk <= core_n_clk; -- for CPOL=1, spi clk has idle HIGH
end generate;
-----------------------------------------------------------------------------------------------
-- Sampling clock enable generation: generate 'samp_ce' from 'core_ce' or 'core_n_ce' depending on CPHA
-- always sample data at the half-cycle of the fsm update cell
383,8 → 381,7
begin
fsm_ce <= core_ce; -- for CPHA=1, latch registers at rising edge of positive core clock enable
end generate;
-----------------------------------------------------------------------------------------------
-- sck enable control: control sck advance phase for CPHA='1' relative to fsm clock
 
sck_ena_ce <= core_n_ce; -- for CPHA=1, SCK is advanced one-half cycle
--=============================================================================================
391,6 → 388,10
-- REGISTERED INPUTS
--=============================================================================================
-- rx bit flop: capture rx bit after SAMPLE edge of sck
--
-- ATTENTION: REMOVING THE FLIPFLOP (DIRECT CONNECTION) WE GET HIGHER PERFORMANCE DUE TO
-- REDUCED DEMAND ON MISO SETUP TIME.
--
rx_bit_proc : process (sclk_i, spi_miso_i) is
begin
if sclk_i'event and sclk_i = '1' then
449,7 → 450,7
end process in_transfer_proc;
 
--=============================================================================================
-- REGISTER TRANSFER PROCESSES
-- RTL REGISTER PROCESSES
--=============================================================================================
-- fsm state and data registers: synchronous to the spi base reference clock
core_reg_proc : process (sclk_i) is
482,7 → 483,7
end process core_reg_proc;
 
--=============================================================================================
-- COMBINATORIAL LOGIC PROCESSES
-- RTL combinatorial LOGIC PROCESSES
--=============================================================================================
-- state and datapath combinatorial logic
core_combi_proc : process ( sh_reg, state_reg, rx_bit_reg, ssel_ena_reg, sck_ena_reg, do_buffer_reg,
495,12 → 496,10
do_transfer_next <= do_transfer_reg; -- output data flag
wr_ack_next <= wr_ack_reg; -- write acknowledge
di_req_next <= di_req_reg; -- prefetch data request
spi_mosi_o <= sh_reg(N-1); -- default to avoid latch inference
state_next <= state_reg; -- next state
spi_mosi_o <= sh_reg(N-1); -- shift out tx bit from the MSb
case state_reg is
when (N+1) => -- this state is to enable SSEL before SCK
-- slave select
spi_mosi_o <= sh_reg(N-1); -- shift out tx bit from the MSb
ssel_ena_next <= '1'; -- tx in progress: will assert SSEL
sck_ena_next <= '1'; -- enable SCK on next cycle (stays off on first SSEL clock cycle)
di_req_next <= '0'; -- prefetch data request: deassert when shifting data
507,8 → 506,6
wr_ack_next <= '0'; -- remove write acknowledge for all but the load stages
state_next <= state_reg - 1; -- update next state at each sck pulse
when (N) => -- deassert 'di_rdy'
-- stretch do_valid
spi_mosi_o <= sh_reg(N-1); -- shift out tx bit from the MSb
di_req_next <= '0'; -- prefetch data request: deassert when shifting data
sh_next(N-1 downto 1) <= sh_reg(N-2 downto 0); -- shift inner bits
sh_next(0) <= rx_bit_reg; -- shift in rx bit into LSb
515,8 → 512,6
wr_ack_next <= '0'; -- remove write acknowledge for all but the load stages
state_next <= state_reg - 1; -- update next state at each sck pulse
when (N-1) downto (PREFETCH+3) => -- if rx data is valid, raise 'do_valid'. remove 'do_transfer'
-- send bit out and shif bit in
spi_mosi_o <= sh_reg(N-1); -- shift out tx bit from the MSb
di_req_next <= '0'; -- prefetch data request: deassert when shifting data
do_transfer_next <= '0'; -- reset transfer signal
sh_next(N-1 downto 1) <= sh_reg(N-2 downto 0); -- shift inner bits
524,8 → 519,6
wr_ack_next <= '0'; -- remove write acknowledge for all but the load stages
state_next <= state_reg - 1; -- update next state at each sck pulse
when (PREFETCH+2) downto 2 => -- raise prefetch 'di_req_o_next' signal and remove 'do_valid'
-- raise data prefetch request
spi_mosi_o <= sh_reg(N-1); -- shift out tx bit from the MSb
di_req_next <= '1'; -- request data in advance to allow for pipeline delays
sh_next(N-1 downto 1) <= sh_reg(N-2 downto 0); -- shift inner bits
sh_next(0) <= rx_bit_reg; -- shift in rx bit into LSb
532,8 → 525,6
wr_ack_next <= '0'; -- remove write acknowledge for all but the load stages
state_next <= state_reg - 1; -- update next state at each sck pulse
when 1 => -- transfer rx data to do_buffer and restart if wren
-- load next word or end transmission
spi_mosi_o <= sh_reg(N-1); -- shift out tx bit from the MSb
di_req_next <= '1'; -- request data in advance to allow for pipeline delays
do_buffer_next(N-1 downto 1) <= sh_reg(N-2 downto 0); -- shift rx data directly into rx buffer
do_buffer_next(0) <= rx_bit_reg; -- shift last rx bit into rx buffer
549,17 → 540,15
state_next <= state_reg - 1; -- update next state at each sck pulse
end if;
when 0 =>
-- idle state: start and end of transmission
di_req_next <= '1'; -- will request data if shifter empty
sck_ena_next <= '0'; -- SCK disabled: tx empty, no data to send
if wren = '1' then -- load tx register if valid data present at di_i
spi_mosi_o <= di_reg(N-1); -- special case: shift out first tx bit from the MSb (look ahead)
ssel_ena_next <= '1'; -- enable interface SSEL
state_next <= N+1; -- start from idle: let one cycle for SSEL settling
spi_mosi_o <= di_reg(N-1); -- special case: shift out first tx bit from the MSb (look ahead)
sh_next <= di_reg; -- load bits from di_reg into shifter
wr_ack_next <= '1'; -- acknowledge data in transfer
else
spi_mosi_o <= sh_reg(N-1); -- shift out tx bit from the MSb
ssel_ena_next <= '0'; -- deassert SSEL: interface is idle
wr_ack_next <= '0'; -- remove write acknowledge for all but the load stages
state_next <= 0; -- when idle, keep this state
599,9 → 588,9
--=============================================================================================
-- DEBUG LOGIC PROCESSES
--=============================================================================================
-- these signals are useful for verification, and can be deleted after debug.
-- these signals are useful for verification, and can be deleted or commented-out after debug.
do_transfer_proc: do_transfer_o <= do_transfer_reg;
state_dbg_proc: state_dbg_o <= std_logic_vector(to_unsigned(state_reg, 4));
state_dbg_proc: state_dbg_o <= std_logic_vector(to_unsigned(state_reg, 6));
rx_bit_reg_proc: rx_bit_reg_o <= rx_bit_reg;
wren_o_proc: wren_o <= wren;
sh_reg_dbg_proc: sh_reg_dbg_o <= sh_reg;
612,5 → 601,5
sck_ena_o_proc: sck_ena_o <= sck_ena_reg;
sck_ena_ce_o_proc: sck_ena_ce_o <= sck_ena_ce;
 
end architecture rtl;
end architecture RTL;
 

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