原创 The Rup and Rdn resistors of StratixII

Q:

In application note an384, it is said that the RUP and RDN resistors are reference resistors used by the calibration circuitry to control the value of the series resistance. Two questions mentioned here:
1. If I use the on-chip series resistance, must I use the calibration circuitry?
2. If I needn't use the calibration circuitry when I use the on-chip series resistance, does the the RUP and RDN resistors necessary yet?

A:

1. Stratix II supports the on-chip series resistance without calibration, but the precision is worse than using calibration.
2. If you don’t use the calibration circuitry, the Rup and Rdn resistors are not necessary, you can use them as general IO, or connect the Rup to VCCIO, and connect Rdn to GND.