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Add sync_reset module and timing constraints

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Alex Forencich 2020-03-27 18:04:04 -07:00
parent f9915b2f31
commit fd1ec1690f
2 changed files with 88 additions and 0 deletions
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57
rtl/sync_reset.v Normal file
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/*
Copyright (c) 2014-2020 Alex Forencich
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
// Language: Verilog-2001
`timescale 1ns / 1ps
/*
* Synchronizes an active-high asynchronous reset signal to a given clock by
* using a pipeline of N registers.
*/
module sync_reset #
(
// depth of synchronizer
parameter N = 2
)
(
input wire clk,
input wire rst,
output wire out
);
(* srl_style = "register" *)
reg [N-1:0] sync_reg = {N{1'b1}};
assign out = sync_reg[N-1];
always @(posedge clk or posedge rst) begin
if (rst) begin
sync_reg <= {N{1'b1}};
end else begin
sync_reg <= {sync_reg[N-2:0], 1'b0};
end
end
endmodule

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syn/sync_reset.tcl Normal file
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# Copyright (c) 2020 Alex Forencich
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
# reset synchronizer timing constraints
foreach inst [get_cells -hier -filter {(ORIG_REF_NAME == sync_reset || REF_NAME == sync_reset)}] {
puts "Inserting timing constraints for sync_reset instance $inst"
# reset synchronization
set reset_ffs [get_cells -quiet -hier -regexp ".*/sync_reg_reg\\\[\\d+\\\]" -filter "PARENT == $inst"]
set_property ASYNC_REG TRUE $reset_ffs
set_false_path -to [get_pins -of_objects $reset_ffs -filter {IS_PRESET || IS_RESET}]
}