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mac: tx: Implement automatic padding

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This also renames the bit_cnt signal to sr_cnt.
97d0905c08 was kinda BS.

This fixes #4.
This commit is contained in:
Markus Koch 2022-01-16 14:44:43 +01:00
parent 22b7d99b1f
commit ef6b6378f8
1 changed files with 31 additions and 19 deletions
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46
trashernet/trashernet_mac.vhd
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@ -33,6 +33,7 @@ end entity trashernet_mac;
architecture rtl of trashernet_mac is
constant ETH_POLYNOMIAL : std_logic_vector(31 downto 0) := x"04C11DB7";
constant ETH_FRAME_MIN_LENGTH : integer := 64;
begin
rx : block
@ -134,12 +135,14 @@ begin
end block rx;
tx : block
type tx_state_t is (IDLE, HEADER, DATA, TXCRC);
type tx_state_t is (IDLE, HEADER, DATA, PAD, TXCRC);
signal tx_state : tx_state_t;
signal sr : byte_vector(0 to mac_in.tx_header.mac_destination'length + mac_in.tx_header.mac_source'length + mac_in.tx_header.mac_ethertype'length - 1);
constant BIT_CNT_MAX : integer := sr'high;
signal bit_cnt : integer range 0 to BIT_CNT_MAX;
constant SR_CNT_MAX : integer := sr'high;
signal sr_cnt : integer range 0 to SR_CNT_MAX;
constant BYTE_CNT_MAX : integer := ETH_FRAME_MIN_LENGTH - 4; -- Minus four because the CRC is *after* the PAD
signal byte_cnt : integer range 0 to BYTE_CNT_MAX;
signal crc : std_logic_vector(ETH_POLYNOMIAL'range);
signal crc_clear : std_logic;
@ -173,40 +176,49 @@ begin
if phy_out.tx_data_ack then
sr <= sr(sr'low + 1 to sr'high) & x"00";
crc_valid <= '1';
if bit_cnt /= 0 then
bit_cnt <= bit_cnt - 1;
if sr_cnt /= 0 then
sr_cnt <= sr_cnt - 1;
end if;
if byte_cnt /= 0 then
byte_cnt <= byte_cnt - 1;
end if;
end if;
case tx_state is
when IDLE =>
when IDLE => -- Idle + prepare sync header
if not phy_out.tx_active and mac_in.tx_mac_data_en then
sr(0 to 7) <= byte_vector'(0 to 6 => x"55", 7 => x"D5");
bit_cnt <= 7;
sr_cnt <= 7;
tx_state <= HEADER;
end if;
when HEADER =>
if (phy_out.tx_data_ack = '1') and (bit_cnt = 0) then -- Sync Header TX complete
when HEADER => -- Wait for sync header + prepare MAC header
if (phy_out.tx_data_ack = '1') and (sr_cnt = 0) then -- Sync Header TX complete
sr <= mac_in.tx_header.mac_destination & mac_in.tx_header.mac_source & mac_in.tx_header.mac_ethertype;
crc_valid <= '1';
bit_cnt <= BIT_CNT_MAX;
sr_cnt <= SR_CNT_MAX;
tx_state <= DATA;
end if;
byte_cnt <= BYTE_CNT_MAX;
when DATA =>
if (phy_out.tx_data_ack = '1') and (bit_cnt = 0) then -- MAC Header TX complete
when DATA => -- Wait for MAC header + transmit payload until tx_mac_data_en goes away
if (phy_out.tx_data_ack = '1') and (sr_cnt = 0) then -- MAC Header TX complete
if mac_in.tx_mac_data_en then
sr(0) <= mac_in.tx_mac_data;
mac_out.tx_mac_data_ack <= '1';
else
sr(0 to 3) <= (crc(7 downto 0), crc(15 downto 8), crc(23 downto 16), crc(31 downto 24));
bit_cnt <= 4 - 1;
tx_state <= TXCRC;
tx_state <= PAD;
end if;
end if;
when TXCRC =>
if (phy_out.tx_data_ack = '1') and (bit_cnt = 0) then -- CRC TX complete
when PAD => -- Wait for PADs / last payload byte + prepare CRC
if (byte_cnt = 0) then
sr(0 to 3) <= (crc(7 downto 0), crc(15 downto 8), crc(23 downto 16), crc(31 downto 24));
sr_cnt <= 4 - 1;
tx_state <= TXCRC;
end if;
when TXCRC => -- Wait for CRC + jump back to idle
if (phy_out.tx_data_ack = '1') and (sr_cnt = 0) then -- CRC TX complete
tx_state <= IDLE;
end if;
end case;