Multiple comparison circuitry for providing a software error trace signal

摘要

Apparatus and method for performing a logical not function in a multi-compare environment is disclosed. By performing two equivalence compares of a measured variable against selectable target values and using the result of the equivalence compares to selectivity set or reset a bistable element, the need for inverting and multiplexing the output of a comparator that is otherwise required when performing a NOT equivalence function in a single-compare environment is eliminated. The not function logic is used in a system analyzer connected to a data processing system and is used to selectively enable the tracing of software execution as a function of whether or not a variable is a predefined value.