Abstract: A data processing arrangement which comprises a memory device provided with a memory with a first field in which memory words are stored or can be stored and a second field in which an error protection bit can be stored for every memory word from the first field. The memory device further comprises an error protection bit generator for the generation of error protection bits and a coincidence circuit. This coincidence circuit operates in two different modes, on the one hand, an error protection mode in which error protection operations, suh as for example the use of parity bits, take place in the known manner and, on the other hand, a coincidence mode in which the error protection operations are suppressed and replaced by coincidence operations. These coincidence operations make it possible to find out whether access operations are being performed at pre-determined memory addresses.

Abstract: A communication system is described for the transfer of messages between a source device and a destination device. There is provided an end-around coupled series of storage control sections, it being possible to chain a non-branching series of messages to each section. There is provided a "busy/not-busy" indicator, a pointer mechanism for indicating a current storage control section for each of the devices, and a notification device which enables the source device with a "signal" in order to signal an activity. Suitable control prevents deadlock and also individual starvation situations.