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    /spi_master_slave/trunk/syn
    from Rev 14 to Rev 16
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Rev 14 → Rev 16

/spi_master.vhd
146,6 → 146,7
-- 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.
-- 2011/08/04 v1.15.0136 [JD] Fixed assertions (PREFETCH >= 1) and minor comment bugs.
--
-----------------------------------------------------------------------------------------------------------------------
-- TODO
283,19 → 284,19
-- minimum word width is 8 bits
assert N >= 8
report "Generic parameter 'N' (shift register size) needs to be 8 bits minimum"
severity FAILURE;
severity FAILURE;
-- minimum prefetch lookahead check
assert PREFETCH >= 2
assert PREFETCH >= 1
report "Generic parameter 'PREFETCH' (lookahead count) needs to be 1 minimum"
severity FAILURE;
severity FAILURE;
-- maximum prefetch lookahead check
assert PREFETCH <= N-5
report "Generic parameter 'PREFETCH' (lookahead count) out of range, needs to be N-5 maximum"
severity FAILURE;
severity FAILURE;
-- SPI_2X_CLK_DIV clock divider value must not be zero
assert SPI_2X_CLK_DIV > 0
report "Generic parameter 'SPI_2X_CLK_DIV' must not be zero"
severity FAILURE;
severity FAILURE;
 
--=============================================================================================
-- CLOCK GENERATION
498,8 → 499,8
spi_mosi_o <= sh_reg(N-1); -- default to avoid latch inference
state_next <= state_reg; -- next state
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)
506,8 → 507,8
di_req_next <= '0'; -- prefetch data request: deassert when shifting data
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
when (N) => -- deassert 'di_rdy' and 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
514,17 → 515,17
sh_next(0) <= rx_bit_reg; -- shift in rx bit into LSb
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
when (N-1) downto (PREFETCH+3) => -- remove 'do_transfer' and shift bits
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
do_transfer_next <= '0'; -- reset 'do_valid' transfer signal
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
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
when (PREFETCH+2) downto 2 => -- raise prefetch 'di_req_o' signal
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
531,8 → 532,8
sh_next(0) <= rx_bit_reg; -- shift in rx bit into LSb
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
when 1 => -- transfer rx data to do_buffer and restart if new data is written
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
548,8 → 549,8
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
end if;
when 0 =>
-- idle state: start and end of transmission
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
564,6 → 565,7
wr_ack_next <= '0'; -- remove write acknowledge for all but the load stages
state_next <= 0; -- when idle, keep this state
end if;
when others =>
state_next <= 0; -- state 0 is safe state
end case;
/spi_slave.vhd
119,6 → 119,7
-- 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.
-- 2011/08/04 v2.02.0121 [JD] Changed minor comment bugs in the combinatorial fsm logic.
--
--
-----------------------------------------------------------------------------------------------------------------------
336,8 → 337,7
state_next <= state_reg; -- fsm control state
case state_reg is
when (N) =>
-- stretch do_valid
when (N) => -- deassert 'di_rdy' and stretch do_valid
wr_ack_next <= '0'; -- acknowledge data in transfer
di_req_next <= '0'; -- prefetch data request: deassert when shifting data
tx_bit_next <= sh_reg(N-1); -- output next MSbit
345,9 → 345,8
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
when (N-1) downto (PREFETCH+3) => -- remove 'do_transfer' and shift bits
do_transfer_next <= '0'; -- reset 'do_valid' transfer signal
di_req_next <= '0'; -- prefetch data request: deassert when shifting data
wr_ack_next <= '0'; -- remove data load ack for all but the load stages
tx_bit_next <= sh_reg(N-1); -- output next MSbit
355,8 → 354,7
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
when (PREFETCH+2) downto 3 => -- raise prefetch 'di_req_o' signal
di_req_next <= '1'; -- request data in advance to allow for pipeline delays
wr_ack_next <= '0'; -- remove data load ack for all but the load stages
tx_bit_next <= sh_reg(N-1); -- output next MSbit
364,8 → 362,7
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
when 2 => -- transfer received data to do_buffer_reg on next cycle
di_req_next <= '1'; -- request data in advance to allow for pipeline delays
wr_ack_next <= '0'; -- remove data load ack for all but the load stages
tx_bit_next <= sh_reg(N-1); -- output next MSbit
375,8 → 372,7
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
when 1 => -- transfer rx data to do_buffer and restart if new data is written
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
tx_bit_next <= di_reg(N-1); -- first output bit comes from the MSb of parallel data
390,7 → 386,7
state_next <= 0; -- next state is idle state
end if;
when 0 =>
when 0 => -- idle state: start and end of transmission
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

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