Entity: sync_Bits_Xilinx

Diagram

positive BITS std_logic_vector INIT T_MISC_SYNC_DEPTH SYNC_DEPTH std_logic Clock std_logic_vector(BITS - 1 downto 0) Input std_logic_vector(BITS - 1 downto 0) Output

Description

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Authors: Patrick Lehmann

Entity: sync_Bits_Xilinx

Description:

This is a multi-bit clock-domain-crossing circuit optimized for Xilinx FPGAs. It utilizes two FD instances from UniSim.vComponents. If you need a platform independent version of this synchronizer, please use PoC.misc.sync.Flag, which internally instantiates this module if a Xilinx FPGA is detected.

.. ATTENTION: Use this synchronizer only for long time stable signals (flags).

CONSTRAINTS: This relative placement of the internal sites are constrained by RLOCs.

Xilinx ISE UCF or XCF file: .. code-block:: VHDL

   NET "*_async"    TIG;    INST "*FF1_METASTABILITY_FFS" TNM = "METASTABILITY_FFS";    TIMESPEC "TS_MetaStability" = FROM FFS TO "METASTABILITY_FFS" TIG;

Xilinx Vivado xdc file: The XDC file sync_Bits_Xilinx.xdc must be directly applied to all instances of sync_Bits_Xilinx. To achieve this, set the property SCOPED_TO_REF to sync_Bits_Xilinx within the Vivado project. Load the XDC file defining the clocks before that XDC file by using the property PROCESSING_ORDER.

.. literalinclude:: ../../../ucf/misc/sync/sync_Bits_Xilinx.xdc :language: xdc :tab-width: 2 :linenos: :lines: 4-8

License:

Copyright 2007-2016 Technische Universitaet Dresden - Germany Chair of VLSI-Design, Diagnostics and Architecture

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and

limitations under the License.

Generics

Generic name Type Value Description
BITS positive 1 number of bit to be synchronized
INIT std_logic_vector x"00000000" initialization bits
SYNC_DEPTH T_MISC_SYNC_DEPTH T_MISC_SYNC_DEPTH'low generate SYNC_DEPTH many stages, at least 2

Ports

Port name Direction Type Description
Clock in std_logic output clock domain
Input in std_logic_vector(BITS - 1 downto 0) @async: input bits
Output out std_logic_vector(BITS - 1 downto 0) @Clock: output bits