82375EB datasheet(73/131 Pages) INTEL

73 / 131 page

82375EBSB

290477 – 52

Figure 10 Fastest PCI Write to PCEB

516 CONFIGURATION CYCLES

One of the requirements of the PCI specification is that upon power up PCI agents do not respond to any

address The only access allowed is through the IDSEL configuration mechanism The PCEB is an exception

to this since it controls access to the BIOS boot code All PCEBESC subsystem addresses that are enabled

after reset are accessible immediately after power up

The configuration read or write command is used to configure the PCEB During the address phase of the

configuration read or write cycle the PCEB samples its IDSEL (ID select) signal (not the address lines) to

generate DEVSEL

In this way IDSEL acts as a chip select During the address phase AD 72 are used to

select a particular configuration register and BE 30 to select a particular byte(s) The PCEB only responds to

configuration cycles if AD 10 e 00 Reference Figure 11 for configuration reads and writes Note that IDSEL

is normally a ‘‘don’t care’’ except during the address phase of a transaction Upon decode of a configuration

cycle and sampling IDSEL active the PCEB responds by asserting DEVSEL

and TRDY

An unclaimed

configuration cycle is never forwarded to the EISA Bus

Configuration cycles are not normally run in burst mode If this happens the PCEB splits the transfer into

single cycles using the slave termination mechanism

82375EB датащи(PDF) 73 Page - Intel Corporation