modules/*/wb_acq_core/acq_fc_fifo.vhd: fix acquisition counter limit

Previously we were counting up to lmt_pkt_size, but after the FIFOs, we aggregate the data. So, we should be counting up to lmt_pkt_size_aggd. Although the end of transaction flags were still correctly asserted (acq_cnt module was still receiving the correct limit lmt_pkt_size_aggd), this could led to miscounting on subsequent acquisitions.

modules/*/wb_acq_core/acq_fc_fifo.vhd: fix acquisition counter limit
Previously we were counting up to lmt_pkt_size, but after the FIFOs, we aggregate the data. So, we should be counting up to lmt_pkt_size_aggd. Although the end of transaction flags were still correctly asserted (acq_cnt module was still receiving the correct limit lmt_pkt_size_aggd), this could led to miscounting on subsequent acquisitions.
4c360e95 · Lucas Russo · 8ffd6150 · 4c360e95
Commit 4c360e95 authored Jan 13, 2016 by Lucas Russo
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Showing with 11 additions and 3 deletions

acq_fc_fifo.vhd hdl/modules/dbe_wishbone/wb_acq_core/acq_fc_fifo.vhd +11 -3

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--- a/hdl/modules/dbe_wishbone/wb_acq_core/acq_fc_fifo.vhd
+++ b/hdl/modules/dbe_wishbone/wb_acq_core/acq_fc_fifo.vhd
@@ -422,7 +422,15 @@ begin
        -- Current channel ID FIFO input
        fifo_fc_id_din <= std_logic_vector(lmt_curr_chan_id);

-        -- Change the FIFO buffer when the previous one has been written
+        -- Change the FIFO buffer when the previous one has been written.
+        --
+        -- WARNING: If the fifo_fc_mux_cnt signal is not zero at the end of transaction,
+        -- it means we have a problem in the transaction, typically an unaligned
+        -- trigger detection (trigger asserted in a atom that is not the last one).
+        -- We have this limitation as we aggregate atoms into a sample prior to
+        -- transferring it to the next module. So a fifo_fc_mux_cnt not zero means
+        -- we have atoms not belonging in that transaction.
+        -- TODO: assert error to user if that condition is detected
        if fifo_fc_mux_inc = '1' then
          fifo_fc_mux_cnt <= fifo_fc_mux_cnt + 1;

@@ -703,9 +711,9 @@ begin

  -- Only count when in pre_trigger or post_trigger and we haven't acquire
  -- enough samples
-  fifo_pkt_cnt_en <= '1' when (unsigned(dbg_pkt_ct_cnt) < lmt_pre_pkt_size and
+  fifo_pkt_cnt_en <= '1' when (unsigned(dbg_pkt_ct_cnt) < lmt_pre_pkt_size_aggd and
                                fifo_fc_data_id(c_fc_payload_ratio(to_integer(lmt_curr_chan_id))-1) = "010") or -- Pre-trigger
-                                (unsigned(dbg_pkt_ct_cnt) < lmt_full_pkt_size and
+                                (unsigned(dbg_pkt_ct_cnt) < lmt_full_pkt_size_aggd and
                                fifo_fc_data_id(c_fc_payload_ratio(to_integer(lmt_curr_chan_id))-1) = "100") -- Post-trigger
                            else '0';