[U-Boot-Users] IceCube MPC5200 PCI crash - need help

[Martin Krause]

wd at denx.de wrote on Wednesday, November 30, 2005 11:48 AM:
> In message
> <47F3F98010FF784EBEE6526EAAB078D1C05EE2 at tq-mailsrv.tq-net.de> you
> wrote:  
> > 
> > Is your PCI card a real 3,3 V card? The IceCube (Lite5200) board
> > only supports 3,3 V cards. No 5,0 V cards and no 3,3 V/5 V mixed
> > cards are allowed.
> 
> That's not correct. 3.3/5V combo-cards work fine.

OK, my formulation was bad.

According to the PCI specification this _should_ work. But there
are PCI cards around with a 5 V key and a 3,3 V key (= combo-cards)
wich drive 5 V on the PCI signals. Those cards are not compliant to
the PCI spec, and could damage a 3,3 V only PCI board.

On the IceCube board the signal levels on the PCI bus must not exceed
3,3 V, because the PCI pins of the MPC5200 are not 5 V tolerant. So 
it must be assured that a 3,3 V/5 V combo-card drives the PCI pins only
with 3,3 V. Otherwis it _may_ work for a while (because the 5 V are 
shortend by the clamp diodes in the MPC5200 down to 3,3 V), but damage
the board sooner or later.

Regards,
Martin