The control path (highlighted in blue in the preceding block diagram) is the same as in the PL master kernels; however, the CSR module syncs with a data slave RAM module. The AI Engine writes output data to a data slave RAM module through an AXI4-Stream interface. The AI Engine application writes output data from downlink and uplink subgraphs to the dlbf_slave and ulbf_slave PL kernels this way. The PL slaves must follow a certain execution flow to function.