Started working on the pipelined Montgomery modular multiplier. Currently can

do the "square" part of the multiplication, i.e. compute the twice larger
intermediate product AB = A * B.

1 files changed, 93 insertions, 0 deletions

diff --git a/rtl/modexpng_mem.v b/rtl/modexpng_mem.v
new file mode 100644
index 0000000..ca89214
--- /dev/null
+++ b/rtl/modexpng_mem.v
@@ -0,0 +1,93 @@
+//
+// TODO: Add license text!
+//
+
+module modexpng_mem #
+(
+    parameter MEM_WIDTH     = 17,
+    parameter MEM_ADDR_BITS =  6
+)
+(
+    input   clk,
+
+    input  [MEM_ADDR_BITS-1:0] a_addr,
+    input                      a_en,
+    input                      a_wr,
+    input  [MEM_WIDTH    -1:0] a_in,
+    output [MEM_WIDTH    -1:0] a_out,
+
+    input  [MEM_ADDR_BITS-1:0] b_addr,
+    input                      b_en,
+    input                      b_reg_en,
+    output [MEM_WIDTH    -1:0] b_out
+);
+
+
+    //
+    // BRAM
+    //
+    (* RAM_STYLE="BLOCK" *)
+    reg [MEM_WIDTH-1:0] bram[0:(2**MEM_ADDR_BITS)-1];
+
+
+    //
+    // Initialization for Simulation
+    //
+    /*
+    integer c;
+    initial begin
+        for (c=0; c<(2**MEM_ADDR_BITS); c=c+1)
+        bram[c] = {MEM_WIDTH{1'b0}};
+    end
+    */
+
+
+
+    //
+    // Output Registers
+    //
+    reg [MEM_WIDTH-1:0] bram_b;
+    reg [MEM_WIDTH-1:0] bram_b_reg;
+
+    assign a_out = 32'hDEADCE11;
+    assign b_out = bram_b_reg;
+
+    
+    //
+    // Note, that when both ports are accessing the same location, conflict can
+    // potentionally arise. See Xilinx UG473 (pages 19-20, "Conflict
+    // Avoidance") for more information. In our configuration to avoid that the
+    // write port must be coded to operate in READ_FIRST mode. If the write
+    // port is overwriting the same address the read port is accessing, the 
+    // write port must read the previously stored data (not the data it is
+    // writing, as that would be WRITE_FIRST mode).
+    //
+
+
+    //
+    // Write-Only Port A
+    //
+    always @(posedge clk)
+        //
+        if (a_en)
+            //
+            if (a_wr) bram[a_addr] <= a_in;
+
+
+    //
+    // Read-Only Port B
+    //
+    always @(posedge clk)
+        //
+        if (b_en)
+            //
+            bram_b <= bram[b_addr];
+
+    always @(posedge clk)
+        //
+        if (b_reg_en)
+            //
+            bram_b_reg <= bram_b;
+
+
+endmodule