Browse Prior Art Database

Serial Diagnostic Link for PS/2 Model 95 Processor Cards

IP.com Disclosure Number: IPCOM000114082D
Original Publication Date: 1994-Nov-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 142K

Publishing Venue

IBM

Related People

Dombrowski, C: AUTHOR [+4]

Abstract

Disclosed is a Serial Diagnostic Link (SDL) for the PS/2* Model 90 and 95 information panel, allowing the main system processor direct access to the alphanumeric display. This display is used during Power-On Self-Test and during error conditions, as information regarding the execution of the processor is reported to the user. With the SDL, the main processor does not have to rely on the operational condition of any other system function to display information on the alphanumeric display. Without the SDL, the Model 95 information panel interface can be used by the main processor only when the Micro Channel*, the planar board VLSI, and the processor complex card interface are the functional.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 50% of the total text.

Serial Diagnostic Link for PS/2 Model 95 Processor Cards

      Disclosed is a Serial Diagnostic Link (SDL) for the PS/2* Model
90 and 95 information panel, allowing the main system processor
direct access to the alphanumeric display.  This display is used
during Power-On Self-Test and during error conditions, as information
regarding the execution of the processor is reported to the user.
With the SDL, the main processor does not have to rely on the
operational condition of any other system function to display
information on the alphanumeric display.  Without the SDL, the Model
95 information panel interface can be used by the main processor only
when the Micro Channel*, the planar board VLSI, and the processor
complex card interface are the functional.

      The SDL is a three-signal interface.  Output signals from the
processor card, which are input signals to the information panel used
to program the alphanumeric display, are DISPLAY_STROBE, and
DISPLAY_RESET.  The DISPLAY_SENSE signal is an input to the processor
card from the information panel, which is the logical NOT of the
DISPLAY_STROBE.  The DISPLAY_SENSE signal is used by the processor to
determine the presence of the SDL and to provide a real-time
mechanism for monitoring the SDL itself.  The interface is operated
in a uni-directional mode, with all information emanating from the
processor card.

      Fig. 1 is a schematic diagram showing the address/write contol
logic and the read back latch used to provide this function.

Fig. 2 is a schematic diagram showing the data deserializer used to
provide this function.

      The support hardware on the processor card and on the
information panel for this function is minimal.  On the processor
card, this logic provides two bits in an I/O WRITE port,
corresponding to the DISPLAY_STROBE and DISPLAY_RESET signals, and
one bit in an I/O READ port, corresponding to the DISPLAY_SENSE
signal.  The operation of these signals by the processor is done
entirely with software.  On the display panel, logic transforms the
incoming SDL bit stream into the existing parallel interrace to
remain compatible with the alphanumeric display.

      Fig. 3 is a timing chart showing the timing of each signal to
display a character on the alphanumeric display.  The duration of
signal levels for this interface are defined only by minimums.  Since
these minimums are less than the times available in processor card
bus cycles, in effect these signals are timing-independent.  No
clocking mechanisms are required for this interface.

      While the timing of the signals is thus independent, the
sequence of their operation is not.  As shown in Fig. 2, five stages
must be performed in the following order---initial, count/latch,
validate/reset, write character, and validate/hold.  The initial
stage is entered on a high-to-low transition of the DISPLAY_RESET
signal.  The state of DISPLAY_STROBE is a "don't care" condition when
ente...