Vitis Model Composer supports importing kernels and graphs as a source blocks (i.e., user-defined functions with no input ports) into the design. These source blocks have inherited sample time and work only when the model has at least one another block with a non-inherited sample time that Simulink can use for sample time propagation. This requires you to add a block (for example a Constant block) in the model and specify a valid sample time. Alternatively, you can explicitly specify the sample time for the imported source blocks similarly to the other source blocks such as Constant, RTP Source blocks etc. from Simulink and AI Engine libraries respectively.
The AIE Kernel, AIE Class Kernel and AIE Graph blocks from the AI Engine/User-Defined Functions library supports importing the code as a source block. When you try to import the kernel into the Vitis Model Composer that has only output ports, the tool identifies that as a source block and adds the Sample time parameter to the Function tab in Block Parameters dialog box as shown in the following figure.
The default value of the Sample time
-1 which indicates the sample time is inherited.
Valid sample time values must be positive, real scalar, or -1.