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https://opencores.org/ocsvn/uart_fiber/uart_fiber/trunk
Subversion Repositories uart_fiber
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/uart_fiber
- from Rev 10 to Rev 11
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Rev 10 → Rev 11
/trunk/Version2/TX_to_spdif_full.vhd
0,0 → 1,117
library IEEE; |
use IEEE.STD_LOGIC_1164.ALL; |
use IEEE.STD_LOGIC_ARITH.ALL; |
use IEEE.std_logic_unsigned.all; |
--use IEEE.NUMERIC_STD.ALL; |
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entity TX_to_spdif_full is |
Port ( iCLK : in STD_LOGIC; |
TX : in STD_LOGIC; |
optic_out : out STD_LOGIC; |
period01 : in STD_LOGIC_VECTOR(6 downto 0); |
periodA : in STD_LOGIC_VECTOR(6 downto 0); |
period10 : in STD_LOGIC_VECTOR(6 downto 0); |
period : in STD_LOGIC_VECTOR(6 downto 0); |
baud_div : in STD_LOGIC_VECTOR(6 downto 0) |
); |
end TX_to_spdif_full; |
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architecture Behavioral of TX_to_spdif_full is |
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--output flip-flop |
signal optic_flop:STD_LOGIC:='0'; |
--optic stage |
signal optic_cnt : STD_LOGIC_VECTOR(6 downto 0):=(0=>'1',others=>'0'); --value 0 to 9 (divide 50Mhz/10=5Mhz) |
signal optic_bit:STD_LOGIC; |
--input stage |
signal tx_cnt : STD_LOGIC_VECTOR(6 downto 0); --value 0-19 (divide 50Mhz/20=2.5Mhz) |
signal tx_bit:STD_LOGIC:='1'; |
signal start_detected : STD_LOGIC:='0'; |
signal tx_half : STD_LOGIC; --1/2 bit |
signal bit_position : STD_LOGIC_VECTOR(3 downto 0);--value 0-9 (bit position from start to stop) |
--baud division |
signal baud_div_cnt : STD_LOGIC_VECTOR(6 downto 0); |
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begin |
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optic_out<=optic_flop; --output (fiber optic) |
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--generate signal on fiber optic |
optic_stage:process (iCLK) |
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begin |
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if (iCLK'event and iCLK = '1') then |
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if(optic_cnt = period) then |
optic_cnt<=(0=>'1',others=>'0'); |
else |
optic_cnt<=optic_cnt+1; |
end if; |
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if((optic_cnt=period or optic_cnt=periodA) or |
((optic_cnt=period10 or optic_cnt=period01) and optic_bit='1')) then |
optic_flop<=not optic_flop; --2.5Mhz / 1.25Mhz signal for 1 / 0 |
end if; |
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if(optic_cnt=period) then |
optic_bit<=tx_bit; --reload input at baud rate |
end if; |
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end if; |
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end process; |
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--Synchronize input (TX pin) with local clock |
input_stage: process (iCLK,TX) |
begin |
if (iCLK'event and iCLK = '1') then |
if(start_detected='0') then |
if(TX='0') then |
start_detected<='1'; |
tx_cnt<=(0=>'1',others=>'0'); |
bit_position<=(others=>'0'); |
tx_half<='0'; |
baud_div_cnt<=(0=>'1',others=>'0'); |
end if; |
else --start detected=1 |
if(baud_div_cnt=baud_div)then --multiply with baud div |
if(tx_cnt=periodA or tx_cnt=period) then --0.5 bit time |
if(tx_half='0')then |
tx_bit<=TX; --sample every bit time (n+0.5 bit time from start) |
if(TX='1' and bit_position=9 and baud_div/=1)then |
start_detected<='0';--resync early if 2 x baudrate <= optic rate (in this case baudrate could be an approximation) |
end if; |
elsif(tx_half='1')then |
if(bit_position/=9)then |
bit_position<=bit_position+1; |
end if; |
if(bit_position=9 and tx_bit='1') then --stop bit |
bit_position<=(others=>'0'); |
if(TX='1')then |
start_detected<='0';--resync |
end if; |
end if; |
end if; |
tx_half<=not tx_half; --next 1/2 bit |
end if;--tx_cnt |
if(tx_cnt=period)then |
tx_cnt<=(0=>'1',others=>'0'); |
else |
tx_cnt<=tx_cnt+1; |
end if; |
baud_div_cnt<=(0=>'1',others=>'0'); |
else |
baud_div_cnt<=baud_div_cnt+1; |
end if;--baud_div |
end if;--start detected |
end if;--clk event |
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end process; |
end Behavioral; |
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