Browse Prior Art Database

Microprogrammed Tracing Method

IP.com Disclosure Number: IPCOM000075987D
Original Publication Date: 1971-Dec-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Halbach, LA: AUTHOR

Abstract

This method provides efficient program tracing through the use of microprogramming. Desired trace information is recorded on tape by the microprogram in a simpler manner than is possible by conventional software tracing techniques. This is because the microprogram executes and examines the traced program directly in its own environment. Thus, it is not necessary to continually save and restore the registers of the traced program and the tracing program, as is required for each traced instruction when performing tracing by conventional techniques.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 63% of the total text.

Page 1 of 2

Microprogrammed Tracing Method

This method provides efficient program tracing through the use of microprogramming. Desired trace information is recorded on tape by the microprogram in a simpler manner than is possible by conventional software tracing techniques. This is because the microprogram executes and examines the traced program directly in its own environment. Thus, it is not necessary to continually save and restore the registers of the traced program and the tracing program, as is required for each traced instruction when performing tracing by conventional techniques.

As shown in the flow diagram, when tracing is active, a special microprogram is entered prior to execution of an instruction. This microprogram builds output records containing trace information in a buffer and tests for a buffer full condition. When the buffer is full, the program areas and registers which might be affected by the tape I/O routine are saved and that I/O routine is entered. For simplicity, this I/O routine is written in machine language. When the I/O is completed, control is returned to the microprogram which restores the saved main storage areas and registers and continues tracing.

There are several advantages of this tracing method over conventional techniques. First, it is not necessary to maintain a separate instruction counter for the traced program, as is required in software traces. The instruction counter is maintained in hardware as in normal execution. Secondly, i...