Sage-Tips

What is high fanout net synthesis?

High Fanout Net Synthesis (HFNS) is the process of buffering the high fanout nets to balance the load. High Fanout Net is the net which drives more number of loads. The nets which more than these limit are known as High Fanout Nets. Clock nets, reset, scan enable nets are generally considered as High Fanout Nets.

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.

What is high fanout?

High Fan in: A given class designed in such a way that it a high number of other classes can easily consume it. High Fan out: A class should be using lot of other classes.

What is clock tree synthesis in physical design?

CLOCK TREE SYNTHESIS (CTS) CTS is the process of connecting the clocks to all clock pin of sequential circuits by using inverters/buffers in order to balance the skew and to minimize the insertion delay. All the clock pins are driven by a single clock source.

What is fan-in of a logic gate?

Fan-in is the number of inputs a logic gate can handle. This is because the complexity of the input circuitry increases the input capacitance of the device. Using logic gates with higher fan-in will help reducing the depth of a logic circuit.

What is the difference between normal buffer and clock 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.

What does fanout mean in computer science?

Fan-out is a term that defines the maximum number of digital inputs that the output of a single logic gate can feed. When this is the case, a device called a buffer can be used between the TTL gate and the multiple devices it must drive. A buffer of this type has a fan-out of 25 to 30.

What is fan in of 3 input NAND gate?

Fan-in refers to how many inputs a logic gate has. So a 3 input NAND has a fan in of 3. Input capacitance is the capacitance at each input node, which acts as a load for the preceding gate or circuit which is driving it. So, a 3 input NAND would have roughly the same input capacitance at each of its 3 inputs.

What is fan-in and fanout?

Fan-in refers to the maximum number of input signals that feed the input equations of a logic cell. Fan-out refers to the maximum number of output signals that are fed by the output equations of a logic cell.

What is the difference between high fan-out net synthesis & clock tree synthesis?

Understand inter-clock balancing requirements. Difference between High Fan-out Net Synthesis (HFNS) & Clock Tree Synthesis: Clock buffers and clock inverter with equal rise and fall times are used. Whereas HFNS uses buffers and inverters with a relaxed rise and fall times.

What is high fanout net synthesis (hfns)?

So, HFNS is the process of synthesizing other than clock nets, such as reset, scan, test enable nets is called as High Fanout Net Synthesis (HFNS)

What is the difference between hfns and buffers?

Buffers and clock inverter with equal rise and fall times are used. whereas HFNS uses buffers and inverters with a relaxed rise and fall times. HFNS are used mostly for reset, scan enable and other static signals having fanouts. there is not stringent requirement of balancing and power reduction.

What are high fanout Nets in Linux?

High Fanout Nets are the nets which drive more number of load. We set some max fanout limit by using the command set_max_fanout. The nets which have greater than these limit are considered as High Fanout Nets (HFN). Generally clock nets, reset, scan, enable nets are High Fanout Nets.