how to make a frame generator in Simulink ?

Lets say that i want to generate n frames of m length separated by a BYTE (0xFF) used as start and end delimitator

I looked into simulink models and i didnt find any permade blocks for this I started with Random Integer Generator block who generates the bytes in my frames, but i dont know how to separate this sequence of bytes into n frames of length m separated by 0xFF Can someone at least point me to some blocks to start play with ?