Отправлено Dr.Alex 11 ноября 2004 г. 10:41 В ответ на: Можете подсказать URL на PCI 2.2 стандарт? отправлено spa04 10 ноября 2004 г. 21:46

Appendix G
I/O Space Address
Decoding for Legacy Devices

A function that supports a PC legacy function (IDE, VGA, etc.) is allowed to claim those
addresses associated with the specific function when the I/O Space (see Figure 6-2) enable
bit is set.
These addresses are not requested using a Base Address register but are assigned by
initialization software. If a device identifies itself as a legacy function (class code), the
initialization software grants the device permission to claim the I/O legacy addresses by
setting the device’s I/O Space enable bit.
If the device does not own all bytes within a DWORD of a legacy I/O range, it is required
to use AD[1::0] to complete the decode before claiming the access by asserting DEVSEL#.
If a legacy function is addressed by an I/O transaction, but does not own all bytes being
accessed in the DWORD, it is required to terminate the transaction with Target-Abort. An
expansion bus bridge is granted an exception to this requirement when performing
subtractive decode. The bridge is permitted to assume that all bytes within the DWORD
being addressed reside on the expansion bus. This means that the bridge is not required to
check the encoding of AD[1::0], and the byte enables before passing the request to the
expansion bus to complete.

Вот и всё :-)
А ссылка например вот
http://e.1asphost.com/luyu/embedded/embed/pci22.pdf
А ещё лучше вот
http://dsp.neora.ru/standarts/bus/PCI_Rev_30.pdf