1. A circuit for managing formatting of a plurality of packets of a communication protocol, comprising: a plurality of representation blocks, each associated with a respective one of a plurality of descriptors of input and output formats of the packets of the communication protocol, each representation block configured to process a value of the respective descriptor, and at least one of the representation blocks adapted to modify the value of the respective descriptor; wherein the plurality of representation blocks includes a representation block for each field of the packets indicated by the input and output formats, each representation block includes one or more registers for storing the respective descriptor, and each descriptor is descriptive of a field of one of the packets and includes a field identifier and a length value indicative of a length of the field; a distribution block coupled to the representation blocks, wherein for each of the packets input by the circuit in the input format, the distribution block is configured to distribute the value of each descriptor for the packet to the representation block associated with the descriptor and is configured to distribute field values; at least one processing element coupled to the distribution block and respectively coupled to each of the at least one representation block, each processing element configured determine a condition in response to a field value, modify a field value in response to the condition being satisfied, and signal the at least one representation block with the condition; wherein the at least one representation block is configured to modify the value of the respective descriptor in response to the signal from the at least one processing element; and a gather block coupled to the representation blocks, wherein for each of the packets output by the circuit in the output format, the gather block is configured to gather the value of each descriptor for the packet from the representation block associated with the descriptor, gather field values for an output packet in response to descriptors output by the representation blocks, and in response to the at least one of the representation blocks modifying the value of the respective descriptor, change the input format to the output format.