Cdc Entity Reference

This is a simple module to pass a set of signals across a clock domain. More...

Entities
Behavioral	architecture

Libraries
ieee

Use Clauses
std_logic_1164
numeric_std

Generics
Width	integer := 1

Ports
clk1	in	std_logic
		The interface clock line.
signals1	in	std_logic_vector ( Width- 1 downto 0 )
		The signals to pass.
clk2	in	std_logic
		The interface clock line.
reset2	in	std_logic
		The active high reset line.
signals2	out	std_logic_vector ( Width- 1 downto 0 )
		The signals passed.

Detailed Description

This is a simple module to pass a set of signals across a clock domain.

Author

Terry Barnaby (terry.nosp@m..bar.nosp@m.naby@.nosp@m.beam.nosp@m..ltd..nosp@m.uk)

Date

2020-05-18

Version

1.0.0

This is a very simple, low utilisation clock domain crossing unit for a set of signals. There is no specific structure to the signals and with multiple signals their state can appear across the clock domain crossing on separate clock edges. So if multiple signals are passed some form of handshake system is needed on top of this. A simple method of acheiving this would be to have one of the signals be a valid signal that is activated/deactivated one clock cycle after the rest of the signals have changed state. It uses two clock synchronisation registers. Note it doesn't have an integral input clock domain register and thus it expects the input signals to be stable for at least two input clock cycles prior to a valid signal going high.

Note this module requires appropriate timing constraints for the CDC applied. This would normally a set_max_delay or set_false_path constraint on the timing to the sendCdcReg1 and recvCdcReg1 registers.

Copyright

2020 Beam Ltd, Apache License, Version 2.0 Copyright 2020 Beam Ltd 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.

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The documentation for this class was generated from the following file:

• /src/dune/source/DuneNvme/src/Cdc.vhd