Browse Prior Art Database

Peripheral Component Interconnect Daughter Card Configuration

IP.com Disclosure Number: IPCOM000113671D
Original Publication Date: 1994-Sep-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 6 page(s) / 222K

Publishing Venue

IBM

Related People

Nasiff, A: AUTHOR [+3]

Abstract

Disclosed is a means for addressing a daughter card on a Peripheral Component Interconnect (PCI) local bus from a system bus during the configuration process occurring during system initialization, when different configuration spaces need to be supported in spite of limitations to the Programmable Option Select (POS) registers supported supported by the Micro Channel* bus for this purpose.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 31% of the total text.

Peripheral Component Interconnect Daughter Card Configuration

      Disclosed is a means for addressing a daughter card on a
Peripheral Component Interconnect (PCI) local bus from a system bus
during the configuration process occurring during system
initialization, when different configuration spaces need to be
supported in spite of limitations to the Programmable Option Select
(POS) registers supported supported by the Micro Channel* bus for
this purpose.

      As shown in Fig. 1, I/O adapter circuits are placed on an I/O
adapter card 10, such as a graphics adapter card, which is connected
to the processor 12 of a computing system by means of a system bus
14.  Card 10 may be an ISA card or a Micro Channel card, depending on
the nature of system bus 14, which may be either an ISA bus or a
Micro Channel bus.  (In this disclosure, the system bus is considered
to be, for example, a Micro Channel bus).  A daughter card 16 is
attached to adapter card 10, being connected to I/O controller
circuit 18 by means of a local bus 20, designated the PCI bus.  In
this way, the functions supported by the graphics adapter circuits
can be changed by changing the daugheter card 16, supporting, for
example, different types of multi-media functions.  Daughter card 16
may alternately be attached to a planar, or system board (not shown)
including graphics adapter circuits and providing the PCI bus.

      The Programmable Option Select (POS) feature of the Micro
Channel bus provides a means for determining and storing the
configuration of adapter cards installed on the system bus.  Each
different type of adapter card has its own identifying number, which
is stored in the firmware of the card.  These identification numbers
are encoded as four digits and stored as two bytes of data.  This
information is stored in battery-powered CMOS memory and in special
disk files.  During initialization, a comparison is made between
stored configuration information and the cards actually installed, to
ensure the integrity of the stored configuration information [*].

      The PCI architecture allows for 256 bytes of configuration
data, having assignments as indicated in Fig. 2, while the Micro

Channel architecture supports only eight POS registers.  During the
address phase of the configuration cycle for the PCI bus, the eight
least-significant AD lines address the 256-byte configuaration space,
while the least-signficant three address lines of the Micro Channel
bus address the Micro Channel POS registers.  Each PCI slave uses the
Initialization Device Select (IDSEL) line to determine whether it has
been selected during a configuration sequence.  The Micro Channel
uses a CDSETUP (Card Setup) line to signify that the Micro Channel is
doing a configuration sequence, in which the slave receiveing the
CDSETUP signal has been selected.

      Thus, during a PCI configuration cycle, it is necessary to
access individual PCI daughter card devices and to...