29
Terminations
3.3
DDR Driver Compensation
External reference resistors are used to control slew rate and driver impedance. The
DDRIMPCRES (or DDRDRVCRES) resistor directly controls the on-die termination (ODT). The
recommendations are as follows:
•
DDRIMPCRES: controls on-die termination, DDR - 385 ohms, DDRII - 285 ohms. Note that
the closest standard 1% resistors are acceptable
.
•
DDRSLWRCRES: controls slew rate and driver impedance, DDR 845 ohms, DDRII
825 ohms.
With these values the ODT is 150/75 ohms for DDRII and 200/100 ohms for DDR.
Figure 9.
DDR Driver Compensation Circuitry
DDRCRES0
DDRSLWCRES
845 ohms DDR
DDRIMPCRES
385 ohms DDR
825 ohms DDRII
285 ohms DDRII
Summary of Contents for 80331
Page 1: ...Intel 80331 I O Processor Design Guide March 2005 Order Number 273823 003 ...
Page 30: ...Intel 80331 I O Processor Design Guide Terminations 30 This Page Intentionally Left Blank ...
Page 122: ...122 Intel 80331 I O Processor Design Guide Memory Controller ...
Page 136: ...Intel 80331 I O Processor Design Guide Power Delivery 136 This Page Intentionally Left Blank ...