Abstract: A method and apparatus for preventing a data processing system (10) from entering a non-recoverable state. In one form, the present invention uses a pin (40) to indicate whether or not the execution of a non-recoverable instruction is legal. If the pin indicates that the execution of the instruction is legal, then the instruction is executed and the data processing system (10) is placed into a state that requires an external stimulus in order to recover. If the pin indicates that the execution of the instruction is illegal, then the instruction is not permitted to place the data processing system (10) into a state that requires an external stimulus in order to recover. Instead, an internal recovery mechanism is provided which returns the data processing system (10) to normal processing.

Abstract: A paging receiver includes a nonvolatile memory which is readable for controlling the operation of the paging device and is capable of being partitioned into a plurality of regions. A protect means is also included for allowing modification to a selected region of the nonvolatile memory in response to an unlock signal. In a first embodiment, the unlock signal is externally applied to the paging receiver. In a second embodiment, the unlock signal is generated when a predetermined coded signal stored in the paging receiver matches a received coded signal. In a third embodiment, the protect means further includes a switch means to permit the selected region of memory to be modified while preventing other regions of memory to be modified.