Chapter 3

PCI Functional

Description

Chapter 3 is divided into the following sections:

Section 3.1, “PCI Addressing”

Section 3.2, “PCI Cache Mode”

Section 3.3, “Configuration Registers”

3.1PCI Addressing

There are three types of PCI-defined address space:

Configuration space

Memory space

I/O space

3.1.1Configuration Space

Configuration space is a contiguous 256-byte set of addresses dedicated to each “slot” or “stub” on the bus. Decoding C_BE/[3:0] determines if a PCI cycle is intended to access the configuration register space. The IDSEL bus signal is a chip select that allows access to the configuration register space only. Any attempt to access configuration space is ignored unless IDSEL is asserted. The eight lower order address lines and byte enables select a specific 8-bit register. The host processor uses this configuration space to initialize the LSI53C810A.

The lower 128 bytes of the LSI53C810A configuration space hold system parameters while the upper 128 bytes map into the LSI53C810A operating registers. For all PCI cycles except configuration cycles, the LSI53C810A registers are located on the 256-byte block boundary defined by the base address assigned through the configured register.

LSI53C810A PCI to SCSI I/O Processor

3-1

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LSI 53C810A technical manual PCI Addressing, 1 Configuration Space