What is clock tree synthesis?
Clock Tree Synthesis (CTS) is the technique of balancing the clock delay to all clock inputs by inserting buffers/inverters along the clock routes of an ASIC design. As a result, CTS is used to balance the skew and reduce insertion latency.
What is CCD in clock tree synthesis?
2) Concurrent clock and data optimization(CCD) In clock concurrent optimization technique, it optimizes both data and clock path concurrently.
What are SDC constraints associated with clock tree?
SDC constraint checking SDC files define clock and generated clocks. Inadequately defined clocks may result in incomplete or incorrect clock designs. Improperly defined SDC may also result in unbalanced clock trees that will make timing closure difficult.
Why do we need clock tree?
Clock Tree Synthesis is a process which makes sure that the clock gets distributed evenly to all sequential elements in a design. The goal of CTS is to minimize the skew and latency. The placement data will be given as input for CTS, along with the clock tree constraints.
Why is CTS done before routing?
Clock is propagated before routing of signals nets and clock is the only signal nets switches frequently which act as sources for dynamic power dissipation.
What is the difference between clock buffer and normal buffer?
Clock buffers have equal rise and fall time. This prevents duty cycle of clock signal from changing when it passes through a chain of clock buffers. Normal buffers are designed with W/L ratio such that sum of rise time and fall time is minimum. They too are designed for higher drive strength.
Why do we use buffers in a clock tree?
The clock buffers are designed with some special property like high drive strength, equal rise and fall time, less delay and less delay variation with PVT and OCV. Clock buffer has an equal rise and fall time. This prevents the duty cycle of clock signal from changing when it passes through a chain of clock buffers.
Why inverters are used in clock tree?
Inverters, Since the Transition time is less for Inverters. It reduced current flow between VDD and VSS rail and hence Power reduction. Better to use both with all drive strength to get good skew and insertion delay. One other advantage of using inverters in a clock tree is the reduction of duty cycle distortion.
What are the synthesis tools in VLSI?
Synthesis Tool
- Flip-Flop.
- Field Programmable Gate Arrays.
- Compiler.
- Register-Transfer Level.
- Process Synthesis.
- Hardware Description Languages.
What is synthesis tool?
This means that FPGA code provided in high level language such as VHDL or Verilog is converted into logic gates using a synthesis tool. A synthesis tool is a computer program that takes in instructions in the form of hardware description languages as input and generates a synthesized netlist as an output.
Why clock buffer is needed?
– Clock Buffers – an integrated circuit that creates copies or derivatives of a reference clock; – Jitter Attenuators or Jitter Cleaners – an integrated circuit that removes jitter (noise) from a reference clock.
What is the uncertainty of a clock?
Clock uncertainty is the time difference between the arrivals of clock signals at registers in one clock domain or between domains. Pre CTS uncertainty is clock skew, clock Jitter and margin. After CTS skew is calculated from the actual propagated value of the clock.
What is clock buffers?
Clock buffers are fairly straight-forward ICs for distributing multiple copies of a clock to multiple ICs with the same frequency requirements. A buffer’s reference clock can be from a clock generator, an XO or a clock already present. Clock buffers scale from 2 outputs to more than 10 outputs.
What is difference between normal buffer and clock buffer?
Why synthesis is important in VLSI?
Synthesis is a very important process for the designers as it enables them to see how the design will actually look like after fabrication. All parameters including area, timing, power can be reported and checked by the designer beforehand only.
What is synthesis process in VLSI?
Synthesis in VLSI is the process of converting your code (program) into a circuit. In terms of logic gates, synthesis is the process of translating an abstract design into a properly implemented chip.
What is RTL analysis?
In digital circuit design, register-transfer level (RTL) is a design abstraction which models a synchronous digital circuit in terms of the flow of digital signals (data) between hardware registers, and the logical operations performed on those signals.
What is clock skew and jitter?
As an approximation, it is often useful to discuss the total clock timing uncertainty between two registers as the sum of spatial clock skew (the spatial differences in clock latency from the clock source), and clock jitter (meaning the non-periodicity of the clock at a particular point in the network).