Browse Prior Art Database

Address Flow Change Tracing Mechanism

IP.com Disclosure Number: IPCOM000038398D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Davis, GT: AUTHOR [+3]

Abstract

A technique is described whereby an address flow change tracing mechanism is used to trace computer program branch operations for diagnostic purposes, and provides microcode tracing without using large amounts of storage. Since the technique described herein utilizes a microcode trace requiring very little storage, the time required to transfer the trace to a host is reduced. The concept centers around the fact that only changes in the program flow are stored. This enhances the ability to trace a program for unwanted or incorrect branches. In computer technology, having the ability to trace a program, either for debugging purposes or for analysis and enhancement activity, requires the incorporation of a trace mechanism.

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Address Flow Change Tracing Mechanism

A technique is described whereby an address flow change tracing mechanism is used to trace computer program branch operations for diagnostic purposes, and provides microcode tracing without using large amounts of storage. Since the technique described herein utilizes a microcode trace requiring very little storage, the time required to transfer the trace to a host is reduced. The concept centers around the fact that only changes in the program flow are stored. This enhances the ability to trace a program for unwanted or incorrect branches. In computer technology, having the ability to trace a program, either for debugging purposes or for analysis and enhancement activity, requires the incorporation of a trace mechanism. In the prior art, to trace the programming code, every address of every executed instruction had to be stored. The trace was initialized by comparing a "trigger" address to the contents of the address bus. When a comparison match occurred, the trace was started or stopped depending on whether a post- trigger or a pre-trigger was desired. During the actual trace function, all addresses placed on the address bus by the processor's program counter were stored in a trace buffer to be retrieved later for analysis. As a result, the trace buffer was required to be large so as to store the trace. The method described herein eliminates the need for a large trace buffer by storing the current addresses only if the instruction address has changed b...