template class xf::dsp::aie::fir::tdm::fir_tdm_graph - 2024.1 English

Vitis Libraries

Release Date
2024-05-30
Version
2024.1 English
#include "fir_tdm_graph.hpp"

Overview

fir_tdm is a Time-Division Multiplexing (TDM) FIR filter

These are the templates to configure the TDM FIR class. Note: Rounding modes rnd_sym_floor and rnd_sym_ceil are only supported on AIE-ML device.

Note: Margin size should not be included in TP_INPUT_WINDOW_VSIZE.

Note: TP_INPUT_WINDOW_VSIZE must be an integer multiple of number of TDM Channels TP_TDM_CHANNELS .

Note: For SSR configurations (TP_SSR>1), TDM Channels coefficients will be split over multiple paths, in a round-robin fashion.

Parameters:

TT_DATA

describes the type of individual data samples input to and output from the filter function.

This is a typename and must be one of the following:

int16, cint16, int32, cint32, float, cfloat.

TT_COEFF

describes the type of individual coefficients of the filter taps.

It must be one of the same set of types listed for TT_DATA and must also satisfy the following rules:

  • Complex types are only supported when TT_DATA is also complex.
  • TT_COEFF must be an integer type if TT_DATA is an integer type
  • TT_COEFF must be a float type if TT_DATA is a float type.
TP_FIR_LEN is an unsigned integer which describes the number of taps in the filter.
TP_SHIFT

describes power of 2 shift down applied to the accumulation of FIR terms before output.

TP_SHIFT must be in the range 0 to 61.

TP_RND

describes the selection of rounding to be applied during the shift down stage of processing.

Although, TP_RND accepts unsigned integer values descriptive macros are recommended where

  • rnd_floor = Truncate LSB, always round down (towards negative infinity).

  • rnd_ceil = Always round up (towards positive infinity).

  • rnd_sym_floor = Truncate LSB, always round towards 0.

  • rnd_sym_ceil = Always round up towards infinity.

  • rnd_pos_inf = Round halfway towards positive infinity.

  • rnd_neg_inf = Round halfway towards negative infinity.

  • rnd_sym_inf = Round halfway towards infinity (away from zero).

  • rnd_sym_zero = Round halfway towards zero (away from infinity).

  • rnd_conv_even = Round halfway towards nearest even number.

  • rnd_conv_odd = Round halfway towards nearest odd number.

    No rounding is performed on ceil or floor mode variants.

    Other modes round to the nearest integer. They differ only in how they round for values of 0.5.

TP_INPUT_WINDOW_VSIZE

describes the number of samples processed by the graph in a single iteration run.

Samples are buffered and stored in a ping-pong window buffer mapped onto Memory Group banks.

TP_TDM_CHANNELS

describes the number of TDM Channels processed by the FIR.

Each kernel requires storage for all taps and all channels it is required to operate on, i.e. requires storage for: TP_FIR_LEN * TP_TDM_CHANNELS .

TP_NUM_OUTPUTS

sets the number of ports to broadcast the output to.

Note: Dual output ports are not supported at this time.
TP_DUAL_IP

allows 2 stream inputs to be connected to FIR, increasing available throughput.

Note: Dual input ports are not supported at this time.
TP_SSR

specifies the number of parallel input/output paths where samples are interleaved between paths, giving an overall higher throughput.

A TP_SSR of 1 means just one output leg and 1 input phase.

The number of AIE kernels created is equal to TP_SSR .

For SSR configurations (TP_SSR>1), the input data must be split over multiple ports, where each successive sample is sent to a different input port in a round-robin fashion.

Each path will have a dedicated input buffer of size defined by TP_INPUT_WINDOW_VSIZE / TP_SSR .

In addition, TDM Channels coefficients will be split over multiple paths, in a round-robin fashion.

Finally, computed output samples will also be split over SSR number of output paths.

Each path will have a dedicated output buffer of size defined by TP_INPUT_WINDOW_VSIZE / TP_SSR .

TP_SAT

describes the selection of saturation to be applied during the shift down stage of processing.

TP_SAT accepts unsigned integer values, where:

  • 0: none = No saturation is performed and the value is truncated on the MSB side.
  • 1: saturate = Default. Saturation rounds an n-bit signed value in the range [- ( 2^(n-1) ) : +2^(n-1) - 1 ].
  • 3: symmetric = Controls symmetric saturation. Symmetric saturation rounds an n-bit signed value in the range [- ( 2^(n-1) -1 ) : +2^(n-1) - 1 ].
template <
    typename TT_DATA,
    typename TT_COEFF,
    unsigned int TP_FIR_LEN,
    unsigned int TP_SHIFT,
    unsigned int TP_RND,
    unsigned int TP_INPUT_WINDOW_VSIZE,
    unsigned int TP_TDM_CHANNELS = 1,
    unsigned int TP_NUM_OUTPUTS = 1,
    unsigned int TP_DUAL_IP = 0,
    unsigned int TP_SSR = 1,
    unsigned int TP_SAT = 1
    >
class fir_tdm_graph: public graph

// structs

struct first_casc_params

template <
    int dim,
    int firlen = TP_FIR_LEN
    >
struct ssr_params

// fields

kernel m_firKernels[TP_SSR]
port_array <input, TP_SSR> in
port_array <output, TP_SSR> out

Fields

kernel m_firKernels [TP_SSR]

The array of kernels that will be created and mapped onto AIE tiles.

port_array <input, TP_SSR> in

The input data array to the function. This input array is either a window API of samples of TT_DATA type or stream API (depending on TP_API). Note: Margin is added internally to the graph, when connecting input port with kernel port. Therefore, margin should not be added when connecting graph to a higher level design unit. Margin size (in Bytes) equals to TP_FIR_LEN rounded up to a nearest multiple of 32 bytes.

port_array <output, TP_SSR> out

The output data array from the function. This output is either a window API of samples of TT_DATA type or stream API (depending on TP_API). Number of output samples is determined by interpolation & decimation factors (if present).

Methods

getKernels

getKernels overload (1)

kernel* getKernels ()

Access function to get pointer to kernel (or first kernel in a chained and/or SSR configurations). No arguments required.

getKernels overload (2)

kernel* getKernels (int ssrIndex)

Access function to get pointer to an indexed kernel.

Parameters:

ssrIndex an index to the SSR data Path.

getKernelArchs

unsigned int getKernelArchs ()

Access function to get kernel’s architecture (or first kernel’s architecture in a chained configuration).

fir_tdm_graph

fir_tdm_graph (const std::vector <TT_COEFF>& taps)

This is the constructor function for the FIR graph with static coefficients.

Parameters:

taps

a reference to the std::vector array of taps values of type TT_COEFF. Coefficients are expected to be in a form that presents each tap for all TDM channels, followed by next tap for *all TDM channels. For example, a 4 tap, 8 TDM channel vector would look like like the vector below:

{.c++}
 std::vector<int16> taps {
            t30, t31, t32, t33, t34, t35, t36, t37,
            t20, t21, t22, t22, t24, t25, t26, t27,
            t10, t11, t12, t11, t14, t15, t16, t17,
            t00, t01, t02, t00, t04, t05, t06, t07}

where each element tnm represents a ‘’n-th’’ tap for a ‘’m-th’’ TDM channel.