FAULT TOLERANT INTERACTIVE DISPLAY HANDLER
Original Publication Date: 1991-Jun-30
Included in the Prior Art Database: 2004-Apr-05
Xerox Disclosure Journal
In a reprographic system having a user interface capable of displaying textual and icon based information, faulty display commands received by the user interface or display controller may result in the undesirable halting of the system, due to the attempt by the display controller to execute such commands. Generally, these faulty commands are most prevalent during system development, prior to release of the final version of the system control software. The present invention is a means for making the user interface display controller more fault tolerant, by enabling the controller to identify illegal or faulty display commands which are received. In a preferred embodiment, the display controller executes commands passed to it by decomposing the command to determine which item to display (i.e., which icon or text string) from a large block of static data called the display data. In addition, the command may have a numeric quantity that is to be displayed in association with the icon or text. The present invention utilizes a fault handler that is designed to detect and be tolerant of faulty commands to enable the graceful recovery from such commands. More specifically, the system includes a fault detection means and an error reporting means which, when an error is detected, reports the error or fault by sending an error message to the support system (i-e., external printer or dumb terminal). The error message produced includes the origination address of the command, the command number, and additional command identification information as required. In addition, the system subsequently "backs out" of the present command and returns normally to the controller which initiated the command. The advantage of this technique is the ability of the system to display error messages and to recover from faulty commands, thereby enabling the system to continue operation without deleterious effects to the system or its components.