Abstract: A system and method for monitoring and maintaining a plurality of modules are described. Each module of the plurality of modules includes at least one link slave device, and a link controller is connected to link slave devices via a plurality of individual serial, bidirectional connections. The link slave devices and the link controller include protocol logic for communication according to a bidirectional protocol. At predefined time segments and predefined periodicity, the link slave devices drive the corresponding bidirectional link to the controller to provider maintenance information to the controller. At other predefined time segments, the controller drives the bidirectional link to issue commands to the link slave devices.

Abstract: A digital data processing system includes a plurality of central processor units which share and access a common memory through a memory management element. The memory management element permits, inter alia, data in the common memory to be accessed in at least two modes. In the first mode, all central processing units requesting access to a given datum residing in memory are signalled of the datum's existence. In the second mode, only selected central processing units requesting access to a resident datum are notified that it exists, while others requesting access to the datum are signalled that it does not exist. The common memory can include a plurality of independent memory elements, each coupled to and associated with, a respective one of the central processing units. A central processing unit can include a post-store element for effecting the transfer of copies of data stored in its associated memory element to a memory element associated with another central processing unit.