CPU Interface Design Considerations
Timing Requirements
Copyright © 2002 Marvell
CONFIDENTIAL
Doc. No. MV-S300165-00, Rev. A
May 21, 2002, Preliminary
Document Classification: Proprietary Information
Page 93
Figure 44: Test Circuit Results (Cload = 15pf)
OVdd/2 = 1.25V at 3 ns in
. This is marked as the reference point to measure the signal fly time in the
system simulation. The reference point for the rising edge is smaller than the falling edge (2.1 ns), so the reference
point is determined by the falling edge. The fly time is measured from the reference point to the Vil measured on
the load.
The output delay values in the AC timing table of the CPU datasheet are defined for a specific test circuit. This
value includes the rise/fall time of the output. To calculate the signal fly time, the rise/fall time must be measured
and a reference measuring point must be set. The CPU reference point is measured in a similar way as the GT-
64260A, but with a different test circuit.
shows the CPU test circuit (Rload = 50 Ohm).