What is High fanout net Synthesis?

What is High fanout net Synthesis?

High Fanout Nets: Some nets other than clock nets is called HFN. Ex: Reset, Scan Enable etc. During synthesis, We set set_max_fanout to some number. i.e. we are telling the synthesis tool to that more than the max_fanout number treat it as High fanout net , so the tool knows and buffers the nets. naveensai12.

How do I stop high fanout?

Possible suggestions for high fanout signals:

1. Floorplan or LOC the origin and the global buffer of the high fanout signal.
2. Duplicate the driver and tell the synthesis tool not to remove the duplicate logic.
3. Use specific net fanout control on the specific net, if the synthesis tool allows.

What is congestion FPGA?

Routing congestion metrics denote the estimated utilization percentage of routing resources in the vertical and horizontal directions of the tiles on FPGA and a utilization rate of over 100% indicates the potential routing problem around that region.

What is HFNs VLSI?

HFNs are synthesized in front end also…. but at that moment no placement information of standard cells are available… hence backend tool collapses synthesized HFNs. It resenthesizes HFNs based on placement information and appropriately inserts buffer.

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 SLR Xilinx?

Super Logic Region (SLR) A Super Logic Region (SLR) is a single FPGA die slice contained in an SSI device. Active Circuitry. Each SLR contains the active circuitry common to most Xilinx FPGA devices. This circuitry.

What is fanout free circuit?

In a fanout-free circuit, the set of all single-stuck faults on the circuit primary inputs is a dominance-reduced fault list for the circuit. ∎ Thus a test that detects all the single-stuck primary input faults, detects all the internal single-stuck faults as well.

How many high fanout nets are in the design?

Warning: Design contains 8 high-fanout nets. A fanout number of 1000 will be used for delay calculations involving these nets. (TIM-134) How can I find the offending nets?

How to find high fanout Nets in Verilog?

A specific threshold N can also defined using the command: all_high_fanout -net -threshold N The reported high fanout nets are typically clock networks. If that is the case, you will see that the timing reports will have a huge increment in those nets, making timing closure much harder.

How to find high fanout Nets in clock tree?

The reported high fanout nets are typically clock networks. If that is the case, you will see that the timing reports will have a huge increment in those nets, making timing closure much harder. Since the high-fanout issue is resolved during Clock Tree Synthesis of the Place & Route phase those timing reports are too pessimistic.

How to define high fanout threshold in design compiler?

In Design Compiler you can use the command all_high_fanout -nets to obtain a collection of nets that has a fanout value bigger than high_fanout_net_threshold variable, which you can review using the command report_app_var high_fanout_net_threshold. A specific threshold N can also defined using the command: