Modular interface

A packet-based communication system is described for linking a peripheral unit (PU) (40) to the outside world via a communications link (54). The system includes a modular interface unit (MIU) (52) which has a memory (60) shared by processors (42,56) in both the PU (40) and MIU (52). The system employs control packets, read packets and write packets and performs a method for allocating the shared memory (60) that optimizes memory utilization. The system determines a ratio of read to write packets required in the operation of the PU (40), and it ignores that ratio if the communications link (54) will not transmit write packets. If the communication link (54) will transmit write packets, it allocates read and write packet space within the shared memory (60) in accordance with the ratio. The system also includes apparatus for enabling MIU (52) configuration via user/keyboard (46) inputs through the PU (40) with the MIU (52) providing the question and answer messages. This feature allows the PU (40) to adapt to many different communication links, simply by replacement and user configuration of the MIU (52). The system further includes apparatus for rapidly handling network protocol headers. Those headers are stored along with the data packets and when the packet is accessed by the PU (40) from shared memory (60), pointers are employed to enable access of only the data portions of such packets while ignoring the network protocol header portions.