What is clock tree design?
A clock tree is a clock distribution network within a system or hardware design. It includes the clocking circuitry and devices from clock source to destination. The complexity of the clock tree and the number of clocking components used. depends on the hardware design.
What is clock tree optimization process?
CTS Optimization process:
- By buffer sizing.
- Gate sizing.
- Buffer relocation.
- Level adjustment.
- HFN synthesis.
- Delay insertion.
- Fix max transition.
- Fix max capacitance.
What are clock tree types?
Up to now, there have been two main methods of clock distribution for large, high-performance designs: conventional clock-tree synthesis (CTS) and clock mesh. Multisource CTS has emerged as a new method that is a hybrid of these two.
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. When this option is set to true, At clock_opt stage the CCD optimization is performed. This attribute also performs area and power optimization at clock_opt stage.
What is difference between HFN synthesis and CTS?
HFN synthesis is performed on reset/scan enable/test enable, etc… The requirement is usually max_tran , max_cap, and max_fanout. CTS is for the clocks where you specify the clock tree slew and skew as the requirements, and depending on the tool, you also specify insertion delay.
Why is it necessary to gating a clock?
Clock gating is a popular technique used in many synchronous circuits for reducing dynamic power dissipation, by removing the clock signal when the circuit is not in use. Clock gating saves power by pruning the clock tree, at the cost of adding more logic to a circuit.
Which is better buffer or inverter?
In most of the library files, a buffer is the combination of two inverters so we can say that inverter will be having lesser delay than buffer with the same drive strength. Also inverters having more driving capacity than a buffer that’s why most of the libraries preferred inverter over buffer for CTS.
What are clock tree exceptions?
Clock Tree Exceptions
Non- Stop Pin. Exclude Pin. Float Pin. Stop Pin. Don’t Touch Subtree.
What is NVP VLSI?
NVP: Non-uniform Voltage and Pulse width Settings.
What is clock pulling?
Clock pulling refers to making the clock late at the launch stage to fix the hold violations. ( Negative Skewing)
What is STA in VLSI?
Static Timing Analysis (STA) is one of the techniques to verify design in terms of timing. This kind of analysis doesn’t depend on any data or logic inputs, applied at the input pins. The input to an STA tool is the routed netlist, clock definitions (or clock frequency) and external environment definitions.
Why do we check setup before CTS?
Short answer: Setup violation depends on the data path delay while hold violation depends on the clock path delay. Before CTS, clock path is taken as ideal because we don’t have skew and transition numbers of the clock path, but this information is sufficient to perform Setup Analysis .
How do you stop clocks from skewing?
The simplest method to help prevent the short data path problem is to minimize the clock skew by using the low-skew global routing resources for clock signals. Microsemi devices provide various types of global routing resources that significantly reduce skew.
What are the inputs to CTS?
Inputs required for CTS:
- Detailed Placement Database.
- Target for latency and skew if specified.
- Buffers or Inverters for building the clock tree.
- Clock Tree DRC (Max Tran, Max Cap, Max fanout, Max no of buffer levels)
How do you balance a CTS skew?
Using Skew Groups to Improve Skew Balancing
CTS engines usually aim for zero skew by balancing the signal arrival time across all the flops regardless of which level of the clock tree they inhabit.