mips_sys

@@ -533,6 +533,7 @@ BEGIN

     -- TX busmaster read state machine

     p_tx_rd_next: PROCESS(r_tx_pos, r_tx_rem, r_tx_start, r_tx_end,

                           s_txframe_en, s_txbuf_wr_en)

+       VARIABLE v_rem: signed(31 DOWNTO 0);

     BEGIN

         n_tx_pos <= r_tx_pos;

         n_tx_rem <= r_tx_rem;

@@ -541,7 +542,11 @@ BEGIN

             n_tx_rem <= signed(r_tx_end) - signed(r_tx_start);

         ELSIF s_txbuf_wr_en = '1' THEN

             n_tx_pos <= std_logic_vector(unsigned(r_tx_pos) + X"00000004");

-            n_tx_rem <= r_tx_rem - X"00000004";

+            v_rem := r_tx_rem - X"00000004";

+            IF v_rem < X"00000000" THEN

+                v_rem := X"00000000";

+            END IF;

+            n_tx_rem <= v_rem;

         END IF;

     END PROCESS p_tx_rd_next;

@@ -597,7 +602,7 @@ BEGIN

         --         space in buffer

         --   write: write request in write buffer

         v_read  := r_bm_rd = '0' AND r_tx_en = '1' AND

-                   r_tx_rem > X"00000000" AND s_txbuf_wr_rdy = '1';

+                   r_tx_rem /= X"00000000" AND s_txbuf_wr_rdy = '1';

         v_write := s_wrbuf_rd_rdy = '1';

         -- read access

         IF v_read THEN