Re: Question about the initialization of configuration registers

[iachetta@us.ibm.com]

>I have some questions. I'm going to design a PCI master/target device
>chip according to PCI Spec. rev. 2.2. Because this chip can be used in
>many PCI application cards, I think subsystem vendor ID and subsystem ID
>must be changeable by system vendors and these IDs will be used to
>identify the system card in PC Windows system. Therefore, many chips use
>an EEPROM to put them in it. But I'd like to implement a PCI device
>without an EEPROM. Using the boot-ROM program in the application side(not
>PCI side), we can assign the initial values of these configuration
>registers whenever system reset (PCI bus reset) is released.
>
>1) Any problem in this method?
>
>2) I know that PC Windows system can't identify the PCI card using this
>chip until PCI configuration registers are set. But I don't know how much
>time is between PCI bus reset and the BIOS startup(as BIOS startup =
>start time of PCI device identification ). Please let me know the time
>sequence among BIOS startup time, PCI bus reset, and CPU reset. I think
>CPU reset and PCI reset will be released at the same time, and then BIOS
>startup. Right? And can you tell me the interval among the events?

There is no spec'ed time sequence or interval that you can count on.
Simply block (retry) configuration accesses to your device until your
application side ROM gets these IDs setup.

Rich Iachetta
IBM Microelectronics Division -- Austin
World Wide Field Design Center
Phone: 512-838-6305   Tie Line: 678-6305