Re: PERR# and SERR#

[Vashek Weis <vashek@ast.co.il> (by way of Daniel Weaver <dan.weaver@znyx.com>)]

Hello Anand,

PERR# is a bidirectional signal, any PCI agent can generate it or monitor it.

SERR# is a unidirectional signal connected in a wired-OR logical function. 
It may be generated by any PCI agent and the PCI Host (Platform, System 
board)) has to monitor it. Not all cheap platforms implement this.

Best regards,
Vashek
========

>From: Kuriakose, Anand <Anand.Kuriakose@fci.com>
>To: pci-sig@znyx.com <pci-sig@znyx.com>
>Subject: PERR# and SERR#
>Date: Sat, 9 Nov 2002 12:11:22 +0530
>
>Hi experts,
>
>Why are some signals in PCI like TRDY#, IRDY#, FRAME# etc categorised as 
>Sustained tristate signals? What makes them different?
>
>Why is PERR# a STS (sustained tristate signal) signal, while SERR# an 
>open-drain signal?
>
>Does the above difference arise due to the fact that
>
>1)      PERR#  has always a transaction cycle associated with it and SERR#
>         is only partially (for address parity errors and data parity 
> errors in
>         special cycle command and for system errors) and
>2)      SERR# can be asserted by more than one agent at any time while PERR#
>         can be asserted by only one agent (involved in the current 
> transaction) at
>         any time.
>
>Thanks in advance.
>
>Regards,
>Anand.

========
Vashek Weis
Standard Products FAE

Advanced Semiconductor Technology Ltd.
http://www.ast.co.il
mailto:vashek@ast.co.il
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