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axi_spdif_tx: CDC overhaul 

Use common prefix for CDC elements and add the proper constraints to the XDC
file. And add a missing stage to the toggle synchronizers.

Also drop a some unnecessary resets.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
main
Lars-Peter Clausen 2015-04-16 10:50:10 +02:00
parent 9183f2287a
commit 8289262807
2 changed files with 25 additions and 14 deletions
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11
library/axi_spdif_tx/axi_spdif_tx_constr.xdc
View File

@ -1,4 +1,11 @@
set_property ASYNC_REG TRUE \
[get_cells -hier cdc_sync_stage1_*_reg] \
[get_cells -hier cdc_sync_stage2_*_reg]
set_false_path \
-from [get_cells -hier cdc_sync_stage0_*_reg -filter {PRIMITIVE_SUBGROUP == flop}] \
-to [get_cells -hier cdc_sync_stage1_*_reg -filter {PRIMITIVE_SUBGROUP == flop}]
set_false_path \
-from [get_cells -hier spdif_out_reg -filter {PRIMITIVE_SUBGROUP == flop}] \
-to [get_cells -hier spdif_tx_o_reg -filter {PRIMITIVE_SUBGROUP == flop}]

28
library/axi_spdif_tx/tx_encoder.vhd
View File

@ -92,9 +92,11 @@ architecture rtl of tx_encoder is
signal par_vector : std_logic_vector(26 downto 0);
signal send_audio : std_logic;
signal cdc_sync_stage0_tick_counter : std_logic := '0';
signal cdc_sync_stage1_tick_counter : std_logic := '0';
signal cdc_sync_stage2_tick_counter : std_logic := '0';
signal cdc_sync_stage3_tick_counter : std_logic := '0';
signal tick_counter : std_logic;
signal tick_counter_d1 : std_logic;
signal tick_counter_d2 : std_logic;
constant X_PREAMBLE : std_logic_vector(0 to 7) := "11100010";
constant Y_PREAMBLE : std_logic_vector(0 to 7) := "11100100";
@ -149,24 +151,30 @@ begin
DCLK : process (data_clk)
begin
if rising_edge(data_clk) then
tick_counter <= not tick_counter;
cdc_sync_stage0_tick_counter <= not cdc_sync_stage0_tick_counter;
end if;
end process DCLK;
process (up_clk) begin
if rising_edge(up_clk) then
cdc_sync_stage1_tick_counter <= cdc_sync_stage0_tick_counter;
cdc_sync_stage2_tick_counter <= cdc_sync_stage1_tick_counter;
cdc_sync_stage3_tick_counter <= cdc_sync_stage2_tick_counter;
end if;
end process;
tick_counter <= cdc_sync_stage3_tick_counter xor cdc_sync_stage2_tick_counter;
CGEN: process (up_clk)
begin
if rising_edge(up_clk) then
if resetn = '0' or conf_txen = '0' then
clk_cnt <= 0;
tick_counter_d1 <= '0';
tick_counter_d2 <= '0';
spdif_clk_en <= '0';
else
tick_counter_d1 <= tick_counter;
tick_counter_d2 <= tick_counter_d1;
spdif_clk_en <= '0';
if (tick_counter_d1 xor tick_counter_d2) = '1' then
if tick_counter = '1' then
if clk_cnt < to_integer(unsigned(conf_ratio)) then
clk_cnt <= clk_cnt + 1;
else
@ -221,12 +229,8 @@ begin
TXSYNC: process (data_clk)
begin
if (rising_edge(data_clk)) then
if resetn = '0' then
spdif_tx_o <= '0';
else
spdif_tx_o <= spdif_out;
end if;
end if;
end process TXSYNC;
-- State machine that generates sub-frames and blocks