Checking programmed controller operation

摘要

Programmed controllers execute sequences of control functions for controlling a device. External noise can cause controller malfunctions on critically operated devices. Proper sequencing is verified by assigning access key/check codes to particular sequences. A check key code is generated during execution of a sequence only if the sequence is properly executed by the programmed controller. At completion of the control sequence, the generated code is compared with the access or original code for verifying appropriate programmed controller sequencing. Several sequences can be embedded or nested in each other, each having its own check key with the overall sequence also having an independent check key.