13.1.5. Decimating CIC
You can use the DecimatingCIC block in a digital down converter for a radio system or a general purpose DSP application. The coefficients and input data are fixed-point types, and the output is the implied full-precision fixed-point type. You can reduce the precision with a separate Scale block, which can perform rounding and saturation to provide the required output precision.
The DecimatingCIC block supports rate changes from two upwards.
The DecimatingCIC has a lower output sample rate than the input sample rate by a factor D, where D is the decimation factor. Usually, the DecimatingCIC discards (D–1) out of D output samples thus lowering the sample rate by a factor D. The physical implementation avoids performing additions leading to these discarded samples, reducing the filter cost.
|Input rate per channel||Specifies the sampling frequency of the input data per channel measured in millions of samples per second (MSPS).|
|Number of channels||Specifies the number of unique channels to process.|
|Number of stages||Specifies the number of comb and integrator stages.|
|Decimation factor||Specifies the decimation factor 1/(integer). (An integer greater than 1 implies interpolation.)|
|Differential delay||Specifies the differential delay.|
|a||Input||The fixed-point data input to the block. If you request more channels than can fit on a single bus, this signal is a vector. The width in bits is inherited from the input wire.|
|v||Input||Indicates validity of the data input signals. If v is high, the data on the a wire is valid.|
|c||Input||Indicates channel of data input signals. If v is high, c indicates which channel the data corresponds to.|
|bypass||Input||When this input asserts, the input data is zero-stuffed and scaled by the gain of the filter, which is useful during hardware debugging.|
|q||Output||The data output from the block. If you request more channels than can fit on a single bus, this signal is a vector. The width in bits is a function of the input width in bits and the parameterization.|
|v||Output||Indicates validity of data output signals.|
|c||Output||Indicates channel of data output signals.|