From a40c577dcc9a7db667a57aba74668ac5c6737eae Mon Sep 17 00:00:00 2001
From: Paul Selkirk <paul@psgd.org>
Date: Tue, 31 Mar 2015 16:24:39 -0400
Subject: Don't delay register reads in eim_regs.

---
 src/rtl/eim_regs.v | 75 +++++++++++++++++++++++++++---------------------------
 1 file changed, 37 insertions(+), 38 deletions(-)

diff --git a/src/rtl/eim_regs.v b/src/rtl/eim_regs.v
index 09a51dc..5903ee6 100644
--- a/src/rtl/eim_regs.v
+++ b/src/rtl/eim_regs.v
@@ -70,9 +70,9 @@ module comm_regs
    reg [31: 0]          tmp_read_data;
 
    // dummy register to check that you can actually write something
-   reg [31: 0] 		reg_dummy;
+   reg [31: 0]          reg_dummy;
+
 
-   
    //----------------------------------------------------------------
    // Concurrent connectivity for ports etc.
    //----------------------------------------------------------------
@@ -80,43 +80,42 @@ module comm_regs
    
 
    //----------------------------------------------------------------
-   // Access Handler
+   // storage registers for mapping memory to core interface
    //----------------------------------------------------------------
-   always @(posedge clk)
-     //
-     if (rst)
-       reg_dummy <= {32{1'b0}};
-     else if (cs) begin
-        //
-        if (we) begin
-           //
-           // WRITE handler
-           //
-           case (address)
-             ADDR_DUMMY_REG:
-               reg_dummy <= write_data;
-           endcase
-           //
-        end else begin
-           //
-           // READ handler
-           //
-           case (address)
-             ADDR_CORE_NAME0:
-               tmp_read_data <= CORE_NAME0;
-             ADDR_CORE_NAME1:
-               tmp_read_data <= CORE_NAME1;
-             ADDR_CORE_VERSION:
-               tmp_read_data <= CORE_VERSION;
-             ADDR_DUMMY_REG:
-               tmp_read_data <= reg_dummy;
-             //
-             default:
-               tmp_read_data <= {32{1'b0}};  // read non-existent locations as zeroes
-           endcase
-           //
-        end
-        //
+   always @ (posedge clk or posedge rst)
+     begin
+        if (rst)
+          begin
+             reg_dummy <= {32{1'b0}};
+          end
+        else if (cs && we)
+          begin
+             // write operations
+             case (address)
+               ADDR_DUMMY_REG:
+                 reg_dummy <= write_data;
+             endcase
+          end
+     end
+
+   always @*
+     begin
+        tmp_read_data = 32'h00000000;
+
+        if (cs && !we)
+          begin
+             // read operations
+             case (address)
+               ADDR_CORE_NAME0:
+                 tmp_read_data = CORE_NAME0;
+               ADDR_CORE_NAME1:
+                 tmp_read_data = CORE_NAME1;
+               ADDR_CORE_VERSION:
+                 tmp_read_data = CORE_VERSION;
+               ADDR_DUMMY_REG:
+                 tmp_read_data = reg_dummy;
+             endcase
+          end
      end
 
 endmodule
-- 
cgit v1.2.3