Described is a protocol controller that supports calls to a packet subroutine which includes a packet processing engine programmed to retrieve packets from a packet memory and to interpret the packets, a working chain pointer module of the packet processing engine programmed to generate a packet memory address for each packet and a return address register of the working chain pointer module, adapted to store a return packet address. Upon processing a call packet, the packet processor engine instructs the working chain pointer module to save a next packet address of a normal packet flow in the return address register, and instructs the working chain pointer module to generate the packet address to execute the packet routine.