//------------------------------------------------------------------------------
//
// modexpa7_subtractor32_artix7.v
// -----------------------------------------------------------------------------
// Hardware (Artix-7 DSP48E1) 32-bit subtractor.
//
// Authors: Pavel Shatov
//
// Copyright (c) 2016-2017, NORDUnet A/S
//
// 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 modexpa7_subtractor32_artix7
(
input clk,
input ce,
input [31: 0] a,
input [31: 0] b,
output [31: 0] d,
input b_in,
output b_out
);
//
// Lower and higher parts of operand
//
wire [17: 0] bl = b[17: 0];
wire [13: 0] bh = b[31:18];
//
// DSP48E1 Slice
//
/* Operation Mode */
wire [ 3: 0] dsp48e1_alumode = 4'b0011;
wire [ 6: 0] dsp48e1_opmode = 7'b0110011;
/* Internal Product */
wire [47: 0] p_int;
modexpa7_dsp48e1_wrapper dsp_subtractor
(
.clk (clk),
.ce (ce),
.carry (b_in),
.alumode (dsp48e1_alumode),
.opmode (dsp48e1_opmode),
.a ({{16{1'b0}}, bh}),
.b (bl),
.c ({{16{1'b0}}, a}),
.p (p_int)
);
//
// Output Mapping
//
assign d = p_int[31: 0];
assign b_out = p_int[32];
endmodule
//------------------------------------------------------------------------------
// End-of-File
//------------------------------------------------------------------------------
