mips_sys

fix CRC generation during ethernet transmission trigger CRC generator only once per byte get CRC value _after_ last byte
Parent e31652f
Stefan Schuermans

Stefan Schuermans commited on 2012-03-07 21:15:53
Showing 1 changed files, with 11 additions and 6 deletions.

io/eth/txframe.vhd
View file @ af62be0
... ... 
@@ -64,6 +64,7 @@ BEGIN
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                     i_if_data_ack,
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                     i_frame_en, i_frame_data, i_frame_data_en,
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                     s_crc_crc)
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+        VARIABLE v_data: std_logic_vector(31 DOWNTO 0);
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     BEGIN
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         n_state          <= r_state;
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         n_data_cnt       <= r_data_cnt;
... ... 
@@ -117,29 +118,33 @@ BEGIN
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                         ELSE
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                             n_state          <= st_crc;
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                             n_data_cnt       <= 4;
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-                            n_data           <= s_crc_crc;
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                         END IF;
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                     ELSE
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                         n_data_cnt          <= r_data_cnt - 1;
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                         n_data(23 DOWNTO 0) <= r_data(31 DOWNTO 8);
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                     END IF;
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-                END IF;
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-                o_if_data    <= r_data(7 DOWNTO 0);
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-                o_if_data_en <= '1';
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                     s_crc_en    <= '1';
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                     s_crc_start <= r_crc_start;
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                     s_crc_data  <= r_data(7 DOWNTO 0);
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+                END IF;
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+                o_if_data    <= r_data(7 DOWNTO 0);
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+                o_if_data_en <= '1';
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             WHEN st_crc =>
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+                IF r_data_cnt = 4 THEN
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+                    v_data := s_crc_crc; -- get CRC value on first CRC byte
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+                ELSE
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+                    v_data := r_data;
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+                END IF;
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                 IF i_if_data_ack = '1' THEN
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                     IF r_data_cnt = 1 THEN
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                         n_state    <= st_gap;
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                         n_data_cnt <= 12 * 8 * 2; -- 12 octets, x2 because of clk
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                     ELSE
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                         n_data_cnt          <= r_data_cnt - 1;
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-                        n_data(23 DOWNTO 0) <= r_data(31 DOWNTO 8);
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+                        n_data(23 DOWNTO 0) <= v_data(31 DOWNTO 8);
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                     END IF;
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                 END IF;
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-                o_if_data    <= r_data(7 DOWNTO 0);
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+                o_if_data    <= v_data(7 DOWNTO 0);
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                 o_if_data_en <= '1';
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             WHEN st_gap =>
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                 IF r_data_cnt = 1 THEN
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