Filter
Top Products
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—Category
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
HDD February 2007
78 Document Number: 305261, Revision: 004
Figure 29 shows the DDR memory interface of the IXP45X/IXP46X network processors
using x16 devices with Error Correcting Code (ECC). Bank 0 is represented by DDR
devices 1, 3, and 5. Bank 1 is represented by DDR devices 2, 4, and 6. Unused data
inputs on the ECC devices (5 and 6) are pulled to ground through 10-KΩ resistors.
The VTT signal termination used for all signals, except clocks, is a series 60.4-Ω resistor
to a 1.25-V DC power supply designed for DDR memory termination. The appropriate
value for termination resistance should be verified through simulation for the specific
topology as shown in “Simulation Results” on page 90. The supply chosen for this
application was the TPS54672 from Texas Instruments*.
The DDRI_RCVENOUT_N signal must be connected to the DDRI_RCVENIN_N signal
with a trace which is propagation delay length matched to the average delay of the
clock (DDRI_CK[2:0]) plus data (DDRI_DQ[31:0]). A series terminating resistor (R
s
)
should be used to control overshoot and undershoot, as shown in Figure 49 on
page 105.
A resistance value in the 25- to 50-Ω range should be used as it adds minimal
propagation delay to the signal without adversely varying from the CLK plus DQ
propagation delay average. The appropriate value for termination resistance should be
verified through simulation for the specific topology.
The DDRI_RCOMP signal must be terminated through a 20-Ω, 1%, 0.1-W resistor
(R
comp
) to ground. This allows the DDR controller to make temperature and process
adjustments.
Table 28. Supported Memory Configurations
DDR
Device
Density
Device
Width
Number of
DDR Devices
(non-ECC)
Devices
per
Clock
Number of
DDR Devices
(ECC)
Devices
per
Clock
Number
of Banks
Total
Memory Size
128 Mbit x8 4 2,2 5 2,2,1 1 64 Mbyte
128 Mbit x8 8 Driver 10 Driver 2 128 Mbyte
128 Mbit x16 2 1,1 3 1,1,1 1 32 Mbyte
128 Mbit x16 4 2,2 6 2,2,2 2 64 Mbyte
256 Mbit x8 4 2,2 5 2,2,1 1 128 Mbyte
256 Mbit x8 8 Driver 10 Driver 2 256 Mbyte
256 Mbit x16 2 1,1 3 1,1,1 1 64 Mbyte
256 Mbit x16 4 2,2 6 2,2,2 2 128 Mbyte
512 Mbit x8 4 2,2 5 2,2,1 1 256 Mbyte
512 Mbit x8 8 Driver 10 Driver 2 512 Mbyte
512 Mbit x16 2 1,1 3 1,1,1 1 128 Mbyte
512 Mbit x16 4 2,2 6 2,2,2 2 256 Mbyte
1 Gbit x8 4 2,2 5 2,2,1 1 512 Mbyte
1 Gbit x8 8 Driver 10 Driver 2 1 Gbyte
1 Gbit x16 2 1,1 3 1,1,1 1 256 Mbyte
1 Gbit x16 4 2,2 6 2,2,2 2 512 Mbyte