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FIR (Multirate Dataflow)

Last Modified: August 28, 2017

Performs Finite Impulse Response (FIR) filtering.



Input data to filter.

This input supports floating-point and fixed-point numbers. On the host, the default data type of this input is double-precision floating-point.



Result of the filter operation.

The data type of this output matches the input data type if the input data type is floating-point. Fixed-point configurations automatically grow the output data type depending on the configuration of the node and the input type.

FIR Configuration

You can configure the FIR to implement any of the following filter classes:

  • Single-rate
  • Interpolation
  • Decimation
  • Fixed-fractional

You can use the Configure FIR dialog box to enter coefficient values directly or read from a COE file on disk.


If you connect any floating-point wires to the FIR, the editor disables the Design Clock Rate, Throughput, and Range because the FIR runs only a model of the filter algorithm. To configure these options, you must implement the FIR using fixed-point data.

Fixed-Point Implementation

If you do not wire any floating point data to the FIR, the FIR automatically selects an optimized fixed-point implementation. The fixed-point implementation of the FIR attempts to auto-select the least resource-intensive architecture that meets or exceeds the throughput goal you configure.

The FIR automatically constrains input data types. If you input a data type that requires internal values to exceed 64 bits, the FIR node reports an error.

Where This Node Can Run:

Desktop OS: Windows

FPGA: All devices

Web Server: Not supported in VIs that run in a web application

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