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//
// Copyright 2016 Ettus Research, a National Instruments Company
//
// SPDX-License-Identifier: LGPL-3.0-or-later
//
module axi_round #(
parameter WIDTH_IN=17,
parameter WIDTH_OUT=16,
parameter round_to_zero=0, // original behavior
parameter round_to_nearest=1, // lowest noise
parameter trunc=0, // round to negative infinity
parameter FIFOSIZE=0, // leave at 0 for a normal single flop
parameter USE_SAFE_ROUND=1 // ensure rounding does not overflow for positive numbers
) (
input clk,
input reset,
input [WIDTH_IN-1:0] i_tdata,
input i_tlast,
input i_tvalid,
output i_tready,
output [WIDTH_OUT-1:0] o_tdata,
output o_tlast,
output o_tvalid,
input o_tready
);
wire [WIDTH_OUT-1:0] out;
generate
if (WIDTH_IN == WIDTH_OUT) begin
assign o_tdata = i_tdata;
assign o_tlast = i_tlast;
assign o_tvalid = i_tvalid;
assign i_tready = o_tready;
end else begin
wire round_corr, round_corr_trunc, round_corr_rtz, round_corr_nearest,
round_corr_nearest_safe;
wire [WIDTH_IN-WIDTH_OUT-1:0] err;
assign round_corr_trunc = 0;
assign round_corr_rtz = (i_tdata[WIDTH_IN-1] & |i_tdata[WIDTH_IN-WIDTH_OUT-1:0]);
assign round_corr_nearest = i_tdata[WIDTH_IN-WIDTH_OUT-1];
// Detect special case of maximum positive number.
// Rounding up is not possible in this case to avoid a wrap to a negative number.
// This detection can be skipped by setting the parameter USE_SAFE_ROUND to 0.
assign round_corr_nearest_safe = ((WIDTH_IN-WIDTH_OUT > 1) && USE_SAFE_ROUND) ?
((~i_tdata[WIDTH_IN-1] & (&i_tdata[WIDTH_IN-2:WIDTH_IN-WIDTH_OUT])) ? 1'b0 : round_corr_nearest) :
round_corr_nearest;
assign round_corr = round_to_nearest ? round_corr_nearest_safe :
trunc ? round_corr_trunc :
round_to_zero ? round_corr_rtz :
0; // default to trunc
assign out = i_tdata[WIDTH_IN-1:WIDTH_IN-WIDTH_OUT] + round_corr;
assign err = i_tdata - {out,{(WIDTH_IN-WIDTH_OUT){1'b0}}};
axi_fifo #(.WIDTH(WIDTH_OUT+1), .SIZE(FIFOSIZE)) flop
(.clk(clk), .reset(reset), .clear(1'b0),
.i_tdata({i_tlast, out}), .i_tvalid(i_tvalid), .i_tready(i_tready),
.o_tdata({o_tlast, o_tdata}), .o_tvalid(o_tvalid), .o_tready(o_tready),
.occupied(), .space());
end
endgenerate
endmodule // axi_round
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