Systems, methods, and apparatus for communicating datagrams over a serial communication link are provided. A transmitting device generates an address field in a datagram, sets a value of at least one bit in the address field to indicate a number of bytes of data associated with a data frame of the datagram, generates the data frame in the datagram, the data frame including the number of bytes of data, and sends the datagram to a receiving device. A receiving device receives a datagram from a transmitting device, decodes an address field of the datagram to detect a number of bytes of data included in a data frame of the datagram based on a value of at least one bit in the address field, and decodes the data frame to recover the detected number of bytes of data.