Configuring Port Sample Rates - 2022.2 English - UG1483

Vitis Model Composer User Guide (UG1483)
Document ID
UG1483
Release Date
2023-01-13
Version
2022.2 English

The Black Box block supports ports that have different sample rates. By default, the sample rate of an output port is the sample rate inherited from the input port (or ports, if the inputs run at the same sample rate). Sometimes, it is necessary to explicitly specify the sample rate of a port (for example., if the output port rate is different than the block's input sample rate).

Note: When the inputs to a black box have different sample rates, you must specify the sample rates of every output port.

SysgenPortDescriptor provides a method called setRate that allows you to explicitly set the rate of a port.

Note: The rate parameter passed to the setRate method is not necessarily the Simulink® sample rate that the port runs at. Instead, it is a positive integer value that defines the ratio between the desired port sample period and the Simulink® system clock period defined by the Model Composer Hub block dialog box.

Assume you have a model in which the Simulink system period value for the model is defined as 2 sec. Also assume that the example dout port is assigned a rate of 3 by invoking the setRate method as follows: 

dout.setRate(3);

A rate of 3 means that a new sample is generated on the dout port every 3 Simulink system periods. Because the Simulink system period is 2 sec, this means the Simulink sample rate of the port is 3 x 2 = 6 sec.

Note: If your port is a non-sampled constant, you can define it in the configuration M-function using the setConstant method of SysgenPortDescriptor. You can also define a constant by passing Inf to the setRate method.