Pipeline requantization, to ease timing closure.

applications/lofar2/libraries/sdp/src/vhdl/sdp_beamformer_local.vhd

@@ -228,8 +228,10 @@ BEGIN
     g_lsb_w               => c_sdp_W_bf_weight_fraction + g_raw_fraction_w,
     g_lsb_round           => TRUE,       
     g_lsb_round_clip      => FALSE,      
-    g_msb_clip            => FALSE,      
-    g_msb_clip_symmetric  => FALSE,      
+    g_msb_clip            => FALSE,  -- wrap beamlet overflow
+    g_msb_clip_symmetric  => FALSE,
+    g_pipeline_remove_lsb => 1,
+    g_pipeline_remove_msb => 0,  -- no msb clipping, so no need for pipeline
     g_in_dat_w            => c_complex_adder_sum_w,                                                                                               
     g_out_dat_w           => c_sdp_W_beamlet_sum                                                                                              
   )

applications/lofar2/libraries/sdp/src/vhdl/sdp_subband_equalizer.vhd

@@ -74,6 +74,10 @@ ARCHITECTURE str OF sdp_subband_equalizer IS
 
   CONSTANT c_quant_dat_w : NATURAL := g_raw_dat_w - g_raw_fraction_w;
   
+  -- Pipeline requantization to easy timing closure
+  CONSTANT c_pipeline_remove_lsb : NATURAL := 1;
+  CONSTANT c_pipeline_remove_msb : NATURAL := 1;
+
   SIGNAL in_sosi : t_dp_sosi;
   SIGNAL cnt : NATURAL RANGE 0 TO c_sdp_Q_fft * c_sdp_N_sub-1;
   SIGNAL gains_rd_address : STD_LOGIC_VECTOR(c_gain_addr_w-1 DOWNTO 0);
@@ -170,8 +174,10 @@ BEGIN
       g_lsb_w               => c_sdp_W_sub_weight_fraction,
       g_lsb_round           => TRUE,
       g_lsb_round_clip      => FALSE,
-      g_msb_clip            => TRUE,
+      g_msb_clip            => TRUE,  -- clip subband overflow
       g_msb_clip_symmetric  => FALSE,
+      g_pipeline_remove_lsb => c_pipeline_remove_lsb,
+      g_pipeline_remove_msb => c_pipeline_remove_msb,
       g_in_dat_w            => c_gain_out_dat_w,
       g_out_dat_w           => g_raw_dat_w
     )
@@ -193,9 +199,11 @@ BEGIN
       g_lsb_w               => c_sdp_W_sub_weight_fraction + g_raw_fraction_w,
       g_lsb_round           => TRUE,       
       g_lsb_round_clip      => FALSE,      
-      g_msb_clip            => TRUE,      
+      g_msb_clip            => TRUE,  -- clip subband overflow
       g_msb_clip_symmetric  => FALSE,      
-      g_in_dat_w            => c_gain_out_dat_w,                                                                                               
+      g_pipeline_remove_lsb => c_pipeline_remove_lsb,
+      g_pipeline_remove_msb => c_pipeline_remove_msb,
+      g_in_dat_w            => c_gain_out_dat_w,
       g_out_dat_w           => c_quant_dat_w
     )
     PORT MAP (