Apparatus and method for real-time program monitoring via a serial

Abstract

A digital microprocessor having a processor core is provided with trace recording hardware capable of receiving, analyzing and temporarily storing data indicative of program instructions (i.e., instruction types) executed by the processor core and of their respective addresses. The trace recording hardware outputs an abbreviated real-time program trace, containing minimum data necessary to reconstruct a full program trace, via a JTAG port to an external debug host computer where a user may reconstruct the full program trace with reference to a program listing. The abbreviation scheme used by the trace recording hardware is preferably achieved by comparing instruction types received from the processor core to at least one pre-defined instruction type, and abbreviating or discarding the corresponding address information as a function of the particular instruction type. The trace recording hardware may be set into one of two modes by the user. In the first mode, the trace recording hardware stalls the processor core when it reaches its maximum storage capacity for instruction type and/or address data until storage becomes available. In the second mode, when the trace recording hardware becomes full it discards data received from the processor core and stores an overflow indicator. The program trace may be initiated and stopped by the user or by signals internal to the digital microprocessor.