Control Data Rate Using the Ready and Request Ports

Convert a signal from 40 MHz to 100 MHz using the FIR Rate Converter HDL Optimized block. Uses the optional request input signal and ready output signal to control the data rate.

• To represent a system clock rate of 200MHz, the model connects a repeating true-false signal to the request port. This configuration generates output samples at 100 MHz, i.e. every second time step. Alternatively, you can connect this port to the ready port of a downstream block.

• When the block can accept a new input sample on the next time step, it sets the ready output signal to true. The model connects this signal to a waveform source that generates one sample at a time.

Open the Model

Configure the Model

Define the data rate parameters in the InitFcn callback.

Configure the FIR Rate Conversion HDL Optimized block. Use an interpolation factor of 5 and a decimation factor of 2. Use the firmpm function to design an equiripple FIR filter. Select both check boxes to enable the ready and request ports. % In the Data Types group, set the Coefficients data type to fixdt(1,16,15) to accommodate your filter design.

Run the Model and Display Results

Run the model. Use the Logic Analyzer to view the input and output signals of the block. The blue icon in the model indicates streamed signals. Launch the Logic Analyzer from the model's toolbar.

In the Logic Analyzer, note the pattern of request and the resulting validOut signal, and the pattern of ready and the resulting validIn signal.

Generate HDL Code

To generate HDL code from the FIR Rate Converter HDL Optimized block, right-click the block and select Create Subsystem from Selection. Then right-click the subsystem and select HDL Code > Generate HDL Code for Subsystem.

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