Report Number: CS-TR-74-420
Institution: Stanford University, Department of Computer Science
Title: Partially self-checking ciruits and their use in performing logical operations.
Author: Wakerly, John F.
Date: August 1973
Abstract: A new class of circuits called partially self-checking circuits is described. These circuits have one mode of operation called secure mode in which they have the properties of totally self-checking circuits; that is, every fault is tested during normal operation and no fault can cause an undetected error. They also have an insecure mode of operation with the property that any fault which affects a result in insecure mode is tested by some input in secure mode; however, undetected errors may occur in insecure mode. One application of these circuits is in the arithmetic and logic unit of a computer with data encoded in an error-detecting code. While there is no code simpler than duplication which detects single errors in logical operations such as AND and OR, it is shown that there exist partially self-checking networks to perform these operations. A commercially available MSI chip, the 74181 4-bit ALU, can be used in a partially self-checking network to perform arithmetic and logical operations.