Abstract: A communication-efficient change log historian allows workstations having images of a shared memory to remain correlated to the shared memory. The system comprises one or more workstations connected to a microprocessor-based device which includes a memory device. The memory device includes the shared memory, and also stores a memory change list and a memory change index. The memory change list forms a list of changes which have been made to the information stored in the shared memory area, and the change index is indicative of the location of the most recent entry to the memory change list. The workstations maintain an image of the shared memory area, and store workstation change indexes which are indicative of the most recent entry to the memory change list which has also been implemented to respective images of the shared memory area in the workstations.

Abstract: A method and apparatus for synchronizing sequence of digital information packets is disclosed. The sequence of digital information packets is provided from a digital information source at a source rate and is later received by a device having an associated synchronization rate. In a preferred embodiment, a counter increment is determined, and a current information packet and a next information packet are selected from the sequence. The current information packet is received into the device. Upon an occurrence of a synchronization event on the device, the counter increment is subtracted from a counter and the counter is compared to a predetermined threshold. If the counter is less than or equal to the predetermined threshold, then the next information packet is received into the device, a next information packet is selected from the sequence, and a predetermined constant is added to the counter.