Intel 80312 I/O Companion Chip - ECEE

Intel ® 80312 I/O Companion ChipPCI-to-PCI Bridge UnitTable 4-8 is a summary of the I/O address decoding rules for Secondary to Primary I/Otransactions. The ISA Enable pertains to the IOBR/IOLR range.Table 4-8.Secondary to Primary I/O Address Decoding SummaryMaster Enable bitI/O Enable bitISA ModebitPrivateMemorySpaceEnableVGA EnableIn IOBR/IOLRrangeIn SIOBR/SIOLRrangeSecondary to PrimaryIn ISA range(Lower 256 bytes)In ISA range(Upper 768 bytes)In VGA I/O RangeOutside allvalid ranges0 X X X X Ignore1 0 0 0 0 Forward Not Valid Not Valid Not Valid Not Valid Forward1 0 0 0 1 Forward Not Valid Not Valid Not Valid Not Valid Forward1 0 1 0 0 Forward Not Valid Not Valid Not Valid Not Valid Forward1 0 1 0 1 Forward Not Valid Not Valid Not Valid Not Valid Forward1 1 0 0 0 Ignore Not Valid Not Valid Not Valid Not Valid Forward1 1 0 0 1 Ignore Not Valid Not Valid Not Valid Ignore Forward1 1 1 0 0 Forward Not Valid Ignore Forward Not Valid Forward1 1 1 0 1 Forward Not Valid Ignore Forward Ignore Forward1 0 0 1 0 Forward Ignore Not Valid Not Valid Not Valid Forward1 0 0 1 1 Forward Ignore Not Valid Not Valid Not Valid Forward1 0 1 1 0 Forward Ignore Not Valid Not Valid Not Valid Forward1 0 1 1 1 Forward Ignore Not Valid Not Valid Not Valid Forward1 1 0 1 0 Ignore Ignore Not Valid Not Valid Not Valid Forward1 1 0 1 1 Ignore Ignore Not Valid Not Valid Ignore Forward1 1 1 1 0 Forward Ignore Ignore Forward Not Valid Forward1 1 1 1 1 Forward Ignore Ignore Forward Ignore ForwardNote:When ISA is enabled, not all of the I/O addresses defined by the IOBR/IOLR range are forwardedupstream.Developer’s Manual 4-27