Browse Prior Art Database

First Processor Cycle Indicator for Personal Computer Systems

IP.com Disclosure Number: IPCOM000109976D
Original Publication Date: 1992-Oct-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Capps Jr, L: AUTHOR [+9]

Abstract

Described is diagnostic circuit for personal computer (PC) systems. The circuit provides a means of indicating the first cycle of a processor by determining if the computer is capable of executing instruction cycles.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 93% of the total text.

First Processor Cycle Indicator for Personal Computer Systems

       Described is diagnostic circuit for personal computer
(PC) systems.  The circuit provides a means of indicating the first
cycle of a processor by determining if the computer is capable of
executing instruction cycles.

      There can exist situations where a computer system is turned on
and no activity is apparent except that the power-on indicator is
lit.  The concept described herein provides a first cycle indicator
to assist in fault isolation.  The indicator provides a means of
improving serviceability and allows software to be implemented for
further diagnostics.

      The figure shows the first processor cycle indicator circuitry.
Circuit module 74F543 is used to receive signals from the output port
of the computer.  On power-up, the output bit from the output port is
set to 1 through the use of the pullup resistor.  Circuit module
74F125 is gated and enabled from logic module (LM) in conjunction
with the combination of the PWRGOOD, CMD* and RDY* signals.  The LM
enables the 74F125 with the CMD* and the RDY* signals after the
PWRGOOD signal is active.  This assures that a complete processor
cycle has occurred under the proper conditions.  If the three inputs
are active, the LM is latched by the PWRGOOD signal and the 74F125 is
kept enabled.  Once the 74F125 is enabled, the signal from the 74F543
is inverted through the 74F125 and the light emitting diode (LED) is
turned on. ...