| 摘要 |
A diagnostic system coupled to a programmable logic controller (PLC) via a serial data link monitors the operation of apparatus under the control of the PLC. Upon detection of a first event-initiating signal, a central processor unit (CPU) in the diagnostic system initiates a timer. The CPU then awaits receipt of a second confirming action signal representing completion of the event initiated by the first signal. The timer times out after a predetermined time interval determined by an operation parameter of the controlled apparatus. If the second confirming action signal is not received before the timer times out, the CPU provides an alarm signal to a video display such as a cathode ray tube (CRT) for displaying an alarm message. The diagnostic system includes a microprocessor controlled interface circuit for receiving data on the serial data link, a random access memory (RAM) mailbox for storing operation data of the PLC and controlled apparatus, and a main central processing unit (CPU) for determining faults in the operation of the apparatus and for providing appropriate outputs to a video generator/display arrangement for providing an alarm to an operator. The diagnostic system is independent of and passive with respect to the PLC and the apparatus it controls. The diagnostic system provides real time operating data to the operator for diagnosis. |
