add wrapper from wb master interface with 32-bit data port to wb interface with 16-bit data port together with testbench

1 files changed, 125 insertions, 0 deletions

diff --git a/design/interface_wrapper.v b/design/interface_wrapper.v
new file mode 100644
index 0000000..30d2e49
--- /dev/null
+++ b/design/interface_wrapper.v
@@ -0,0 +1,125 @@
+/*
+ * For now, this wrapper ignores SEL_O signals - we'll update it for
+ * byte-granular accesses later.
+ */
+`default_nettype none
+
+module interface_wrapper
+  (
+   input wire 	      CLK_I,
+   input wire 	      RST_I,
+
+   output wire 	      RAW_ACK_I,
+   output wire 	      RAW_ERR_I, /* We'll start using it soon */
+   input wire [20:0]  RAW_ADR_O,
+   output wire [31:0] RAW_DAT_I,
+   input wire [31:0]  RAW_DAT_O,
+   input wire [3:0]   RAW_SEL_O, /* We'll start using it soon */
+   input wire 	      RAW_STB_O,
+   input wire 	      RAW_CYC_O,
+   input wire 	      RAW_WE_O,
+   output wire 	      RAW_STALL_I,
+
+   input wire 	      WRAPPED_ACK_I,
+   output wire [19:0] WRAPPED_ADR_O,
+   input wire [15:0]  WRAPPED_DAT_I,
+   output wire [15:0] WRAPPED_DAT_O,
+   output wire 	      WRAPPED_STB_O,
+   output wire 	      WRAPPED_CYC_O,
+   output wire 	      WRAPPED_WE_O,
+   input wire 	      WRAPPED_STALL_I
+   );
+
+   /* RAW -> WRAPPED */
+   wire 	      wrapped_request_happens;
+   assign wrapped_request_happens = WRAPPED_STB_O && !WRAPPED_STALL_I;
+
+   wire 	      raw_request_wanted;
+   assign raw_request_wanted = RAW_STB_O && RAW_CYC_O;
+
+   reg [19:0] 	      ADR_O_waiting;
+   reg [31:0] 	      DAT_O_waiting;
+   reg 		      WE_O_waiting;
+   reg [1:0] 	      request_out_waiting;
+
+   wire 	      can_accept_request;
+   assign can_accept_request = !request_out_waiting[0] ||
+			       (!request_out_waiting[1] &&
+				wrapped_request_happens);
+
+   assign WRAPPED_ADR_O = request_out_waiting[0] ?
+			  ADR_O_waiting : RAW_ADR_O >> 1;
+   assign WRAPPED_DAT_O = request_out_waiting[0] ?
+			  DAT_O_waiting[15:0] : RAW_DAT_O[15:0];
+   assign WRAPPED_WE_O = request_out_waiting[0] ?
+			 WE_O_waiting : RAW_WE_O;
+   assign WRAPPED_STB_O = request_out_waiting[0] || raw_request_wanted;
+
+   assign WRAPPED_CYC_O = RAW_CYC_O;
+
+   always @ (posedge CLK_I) begin
+      if (RST_I) begin
+	 ADR_O_waiting <= 20'bx;
+	 DAT_O_waiting <= 32'bx;
+	 WE_O_waiting <= 1'bx;
+	 request_out_waiting <= 2'b0;
+      end else begin
+	 if (wrapped_request_happens) begin
+	    if (request_out_waiting[1]) begin
+	       ADR_O_waiting <= ADR_O_waiting + 1;
+	       DAT_O_waiting <= {16'bx, DAT_O_waiting[31:16]};
+	       request_out_waiting <= {1'b0, request_out_waiting[1]};
+	    end else begin
+	       ADR_O_waiting <= RAW_ADR_O >> 1;
+	       WE_O_waiting <= RAW_WE_O;
+	       request_out_waiting[0] <= raw_request_wanted;
+
+	       if (request_out_waiting[0]) begin
+		  ADR_O_waiting <= RAW_ADR_O >> 1;
+		  DAT_O_waiting <= RAW_DAT_O;
+		  request_out_waiting[1] <= raw_request_wanted;
+	       end else begin
+		  ADR_O_waiting <= (RAW_ADR_O >> 1) + 1;
+		  DAT_O_waiting <= {16'bx, RAW_DAT_O[31:16]};
+		  request_out_waiting[1] <= 0;
+	       end
+	    end // else: !if(request_out_waiting[1])
+	 end else if (!request_out_waiting[0]) begin // if (wr_request_happens)
+	    ADR_O_waiting <= RAW_ADR_O >> 1;
+	    WE_O_waiting <= RAW_WE_O;
+	    DAT_O_waiting <= RAW_DAT_O;
+	    request_out_waiting <= {2{raw_request_wanted}};
+	 end
+      end // else: !if(RST_I)
+   end // always @ (posedge CLK_I)
+
+   /* WRAPPED -> RAW */
+   wire 	      wrapped_request_completes;
+   assign wrapped_request_completes = WRAPPED_CYC_O && WRAPPED_ACK_I;
+
+   reg [15:0] 	      DAT_I_waiting;
+   reg 		      DAT_I_received;
+
+   assign RAW_ACK_I = WRAPPED_ACK_I && DAT_I_received;
+   assign RAW_ERR_I = 0; /* We'll start using it soon */
+   assign RAW_DAT_I = {WRAPPED_DAT_I, DAT_I_waiting};
+   assign RAW_STALL_I = !can_accept_request;
+
+   always @ (posedge CLK_I) begin
+      if (WRAPPED_ACK_I)
+	DAT_I_waiting <= WRAPPED_DAT_I;
+
+      if (RST_I)
+	DAT_I_received <= 0;
+      else if (wrapped_request_completes)
+	DAT_I_received <= !DAT_I_received;
+   end
+
+`ifdef SIMULATION
+   /* avoid undefined values */
+   initial begin
+      request_out_waiting <= 0;
+      DAT_I_waiting <= 0;
+   end
+`endif
+endmodule // interface_wrapper