rtl: rework memory controls in accum

rtl/accum/src/accum.sv

@@ -39,10 +39,6 @@ module accumulator
     logic out_valid_reg;
     logic finish_reg, finish_buf;
 
-    // registers for port b data request
-    reg req_data_b;
-    reg [15:0] req_addr_b;
-
     typedef enum logic [3:0] {
         IDLE,
         INIT_MEM,
@@ -58,6 +54,57 @@ module accumulator
     } wr_state_t;
     (* MARK_DEBUG="true" *) wr_state_t wr_state;
 
+    // One word per clock accumulation pipeline
+    // On every sum_valid in ACCUM we launch a BRAM read for cnt_addr
+    // On the next clock the saved sum_data is added to doutb and written back
+    logic accum_pipe_valid;
+    logic [15:0] accum_pipe_addr;
+    logic [ACCUM_WIDTH-1:0] accum_pipe_data;
+
+    // case smp_num // WINDOW_SIZE == 1
+    // Then the next sequence can read the same address it is written
+    logic accum_pipe_bypass_valid;
+    logic [ACCUM_WIDTH-1:0] accum_pipe_bypass_data;
+    logic accum_done;
+
+    logic accum_accept_last;
+    logic accum_accept_last_all;
+    logic [ACCUM_WIDTH-1:0] accum_write_base;
+    logic [ACCUM_WIDTH-1:0] accum_write_value;
+
+    assign accum_accept_last     = (cnt_smp_num + WINDOW_SIZE >= smp_num_reg);
+    assign accum_accept_last_all = accum_accept_last && (cnt_seq_num == seq_num_reg - 1);
+    assign accum_write_base      = accum_pipe_bypass_valid ? accum_pipe_bypass_data : data_bram_out;
+    assign accum_write_value     = accum_pipe_data + accum_write_base;
+
+    // Memory controls to XPM
+    // In accumulation/init states they are driven directly from the current
+    // state and pipeline registers. That avoids an extra register stage
+    logic mem_wea;
+    logic mem_enb;
+    logic [15:0] mem_addra;
+    logic [15:0] mem_addrb;
+    logic [ACCUM_WIDTH-1:0] mem_dina;
+
+    assign mem_wea = (wr_state == INIT_MEM) ? valid_data :
+                     (wr_state == ACCUM)    ? accum_pipe_valid :
+                                              1'b0;
+
+    assign mem_addra = (wr_state == INIT_MEM) ? cnt_addr :
+                       (wr_state == ACCUM)    ? accum_pipe_addr :
+                                                addra;
+
+    assign mem_dina = (wr_state == INIT_MEM) ? data :
+                      (wr_state == ACCUM)    ? accum_write_value :
+                                               data_bram_in;
+
+    assign mem_enb = (wr_state == ACCUM) ? valid_data : enb;
+    assign mem_addrb = (wr_state == ACCUM) ? cnt_addr : addrb;
+
+    // registers for port b data request
+    reg req_data_b;
+    reg [15:0] req_addr_b;
+
     always @(posedge clk_in) begin
         if (rst) begin
             smp_num_reg <= '0;