Re: standard loads on 66 MHz PCI

From: David Haedge <d-haedge@ti.com>
Date: Mon Nov 09 1998 - 07:36:11 PST

We had a similar problem with a Motorola MPC750. The L2 cache MAX timing
numbers are specified to a 20pF load and the MIN numbers to a 5pF load.
We were using ICX to analyze timing. We looked at the output under no load,
then at 20pF and 5pF. The delta was measured to be 477ps. We then adjusted
the timing sheets in ICX so that the minimum allowed routing distance was
effectively increased by 477ps to compensate for the additional 'test' load.
This allowed us to use a single IBIS model with Cref set at 20pF. You may
be able to apply a similar 'trick' with the PCI driver and Vref.

David Haedge
Raytheon Systems Company
Received on Mon Nov 9 07:43:57 1998

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