US 5,608,876 A · Add-in board with enable-disable expansion ROM for PCI bus computers

Abstract

An adapter or add-in card for use in a peripheral component interconnect (PCI) computer includes a universal module which couples the card to the PCI bus. The module includes a set of selectively programmable configuration registers which are loaded by a microprocessor on the adapter. A circuit arrangement on the module issues a command which inhibits the PCI processor from accessing the configuration registers until fully loaded. Another circuit arrangement presents the Expansion ROM base address register as a `read/write` register or a read only register with all bits set to logical "0 " to the PCI computer. If the Expansion ROM base address register is presented as a read only register with all bits set to "0 ", the PCI computer concludes that no Expansion ROM exists on the add-in card, and its contents are not shadowed into the memory of the PCI computer. This disabling of the Expansion ROM causes memory space to be conserved in the computer. If the Expansion ROM is presented as a read/write register with non-zero values, the PCI computer concludes that an Expansion ROM exists and "shadows" its contents into the memory of the PCI computer.

Claims18

Dependent claims

An add-in board for using in a PCI computer system comprising:

a first bus;
a subassembly task generator means, coupled to the first bus, for performing predetermined functions to accomplish a desired task;
a non-volatile storage coupled to the first bus, said non-volatile storage containing an Expansion ROM for storing code to be executed by a processor not connected to the first bus;
an on-board microprocessor coupled to the first bus, said on-board microprocessor configuring the add-in board to allow the processor not connected to the first bus access or no access to the Expansion ROM;
a PCI bus interface chip for interconnecting to the first bus and a second bus, said PCI bus interface chip including at least one control register with at least one bit to be activated by the on-board microprocessor;
a PCI Expansion ROM base address register accessible by the processor not connected to the first bus;
and
a logic means being responsive to the logical state of the at least one bit for allowing a predetermined bit pattern to be outputted from the PCI Expansion ROM base address register wherein the predetermined bit pattern is an indication of no Expansion ROM to the processor not connected to the first bus.

5 more elements

Dependencies are inferred from the claim text.

Add-in board with enable-disable expansion ROM for PCI bus computers

Life of this patent

Add-in board with enable-disable expansion ROM for PCI bus computers

Life of this patent

Abstract

Claims18