//======================================================================
//
// blockmem2r1wptr.v
// -----------------
// Synchronous block memory with two read ports and one write port.
// For port 1 the address is implicit and instead given by the
// internal pointer. But write address is explicitly given.
//
// The memory is used in the modexp core.
//
//
// Author: Joachim Strombergson
// Copyright (c) 2015, NORDUnet A/S All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
// - Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
//
// - Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// - Neither the name of the NORDUnet nor the names of its contributors may
// be used to endorse or promote products derived from this software
// without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
// PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
// TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
//======================================================================
module blockmem2rptr1w(
input wire clk,
input wire reset_n,
input wire [07 : 0] read_addr0,
output wire [31 : 0] read_data0,
output wire [31 : 0] read_data1,
input wire rst,
input wire cs,
input wire wr,
input wire [07 : 0] write_addr,
input wire [31 : 0] write_data
);
//----------------------------------------------------------------
// Memories and regs including update variables and write enable.
//----------------------------------------------------------------
reg [31 : 0] mem [0 : 255];
reg [31 : 0] tmp_read_data0;
reg [31 : 0] tmp_read_data1;
reg [7 : 0] ptr_reg;
reg [7 : 0] ptr_new;
reg ptr_we;
//----------------------------------------------------------------
// Concurrent connectivity for ports etc.
//----------------------------------------------------------------
assign read_data0 = tmp_read_data0;
assign read_data1 = tmp_read_data1;
//----------------------------------------------------------------
// mem_update
//
// Clocked update of memory This should cause
// the memory to be implemented as a block memory.
//----------------------------------------------------------------
always @ (posedge clk)
begin : mem_update
if (wr)
mem[write_addr] <= write_data;
tmp_read_data0 <= mem[read_addr0];
tmp_read_data1 <= mem[ptr_reg];
end
//----------------------------------------------------------------
// reg_update
//----------------------------------------------------------------
always @ (posedge clk or negedge reset_n)
begin : reg_mem_update
if (!reset_n)
ptr_reg <= 8'h00;
else
if (ptr_we)
ptr_reg <= ptr_new;
end
//----------------------------------------------------------------
// ptr_logic
//----------------------------------------------------------------
always @*
begin : ptr_logic
ptr_new = 8'h00;
ptr_we = 1'b0;
if (rst)
begin
ptr_new = 8'h00;
ptr_we = 1'b1;
end
if (cs)
begin
ptr_new = ptr_reg + 1'b1;
ptr_we = 1'b1;
end
end
endmodule // blockmem2r1wptr
//======================================================================
// EOF blockmem2r1wptr.v
//======================================================================
