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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
February 2007 HDD
Document Number: 305261, Revision: 004 97
DDR-SDRAM—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
The simulation results in Figure 42 are for the data circuit with a DDR device using full
drive strength and show that the voltage waveform meets the DDR device input voltage
requirements. V
il(max)
of V
ref
– 0.150 or 1.10 V and V
ih(min)
of V
ref
+ 0.150 or 1.40 V
are easily achieved at the receiver (IXP45X/IXP46X network processors). However, the
receiver waveform must also not exceed a maximum voltage of V
in(max)
= 2.8 V or the
minimum voltage of V
in(min)
= -0.3 V and the waveforms at the IXP45X/IXP46X
network processors are close to these limits. A larger series resistor could be used to
attenuate the signal, but the results of doing so might have an adverse effect on write
operations.
Waveform results for DDR_DEVICE2 are not shown as it is not relevant when reading
from DDR_DEVICE1. Due to the symmetry of the topology, waveform results when
reading from DDR_DEVICE2 would be identical to those when reading from
DDR_DEVICE1. When final routing data is available, simulation results for all receivers
are analyzed as variations in routing may result in differences. These differences should
be minimal.
Figure 42. DDR Data Read Simulation Results: Two-Bank x16 Devices (Full Drive
Strength)