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Look up synchronizer in Wiktionary, the free dictionary. The term synchronizer may refer to: In automobiles, a synchronizer is part of a synchromesh manual transmission that allows the smooth engagement of gears. In aerial warfare, a synchronizer is a device that permits an automatic weapon to fire between the blades of a revolving propeller.
- Synchronization: Why care?
- The Real World
- Metastability
- Mean Time Between Failures
- Synchronizer Requirements
- Dynamic FFs not suitable for synchronizers since they have no regeneration
- 2-phase (or edge based) handshaking is also suitable
- High Bandwidth solutions
- Our pointers change in a very specific way (when they change, they increment by 1)
- Pointer Synchronizer pitfall
- CLK
- Conclusions
- GeneratedCaptionsTabForHeroSec
Digital Abstraction depends on all signals in a system having a valid logic state Therefore, Digital Abstraction depends on reliable synchronization of external events
Real World does not respect the Digital Abstraction! Inputs from the Real World are usually asynchronous to your system clock Inputs that come from other synchronous systems are based on a different system clock, which is typically asynchronous to your system clock
When asynchronous events enter your synchronous system, they can cause bistables to go into metastable states Every real life bistable (such as a D-latch) has a metastable state
For a FF we can compute its MTBF, which is a figure of merit related to metastability.
Synchronizers must be designed to reduce the chances system failure due to metastability Synchronizer requirements Reliable [high MTBF] Low latency [works as quickly as possible] Low power/area impact
CLK CLK D CMOS Dynamic FF Q D TSFF (Svenson) Special ‘SYNC’ FFs should be used for the primary synchronizer if available
Sender outputs data and THEN changes state of REQ, will not change state of REQ again until after ACK changes state. Receiver latches data. Once receiver is ready for more it changes state of ACK. 2-phase requires one bit of state be kept on each side of transaction. Used when FFs are inexpensive and reliable reset is available.
Handshaking works great, but reduces bandwidth at the clock crossing interface because each piece of data has many cycles of series handshaking. Correctly designed FIFOs can increase bandwidth across the interface and still maintain reliable communication
Applying a traditional two stage FF synchronizer on each bit of a binary pointer could cause a wildly invalid pointer value to be produced Gray coding the pointer value means at most one bit will change per cycle – we can only be ‘off by one’ Binary Gray
Write and read pointers need to be registered in gray code as shown on previous slide. Don’t be tempted to cheat and register pointers in binary. What’s wrong with the synchronizer shown below? PTR_IN CLK
Combinational logic frequently contains hazards at the output (non fully covered Karnaugh map) Avoid this problem by using a registered value of PTR_IN CLK
Synchronizers are important. Synchronization failure is deadly and difficult to debug Synchronization requires careful design. Most CAD and logic tools CANNOT catch bad synchronizer designs. Design of synchronizer depends on performance level needed. Basic synchronizer of back-to-back FFs is the core design all others are based on.
Learn how to design synchronizers for reliable and low-latency digital logic circuits using flip flops, handshaking, and FIFOs. This PDF explains the requirements, analysis, and examples of synchronization in digital systems, with a focus on bus synchronization and metastability issues.
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Learn how synchronizers or "synchros" let you shift gears smoothly in your manual-transmission car without double-clutching. Find out how they work and what they look like with diagrams and examples.
May 5, 2020 · by VLSI Universe - May 5, 2020 0. The circuits which accept the input that can change at arbitrary times and produces output with a nonzero probability of Metastability are Synchronizers. The sequential logic elements are mainly characterized by the setup and hold times.
Jul 1, 2005 · Learn how synchronizers work in manual transmissions and transfer cases to prevent gear clash and shift smoothly. The web page explains the theory, design and operation of synchronizer assemblies with diagrams and examples.
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Apr 28, 2024 · Definitions of synchronizer. noun. an instrument that indicates whether two periodic motions are synchronous (especially an instrument that enables a pilot to synchronize the propellers of a plane that has two or more engines) synonyms: synchroniser, synchronoscope, synchroscope. see more.
