EP3C80 datasheet(108/274 Pages) ALTERA

108 / 274 page

6–10

Chapter 6: I/O Features in the Cyclone III Device Family

OCT Support

Cyclone III Device Handbook

July 2012

Altera Corporation

Volume 1

Figure 6–4 shows the external calibration resistors setup on the RUP and RDN pins and

the associated OCT calibration circuitry.

RUP

and RDN pins go to a tri-state condition when calibration is completed or not

running. These two pins are dual-purpose I/Os and function as regular I/Os if you

do not use the calibration circuit.

On-Chip Series Termination Without Calibration

The Cyclone III device family supports driver impedance matching to the impedance

of the transmission line, which is typically 25  or 50 . When used with the output

drivers, OCT sets the output driver impedance to 25  or 50 . The Cyclone III device

family also supports output driver series termination (RS =50 ) for SSTL-2 and

SSTL-18

Figure 6–4. Cyclone III Device Family On-Chip Series Termination with Calibration Setup

Cyclone III Device Family OCT with

Calibration with RUP and RDN pins

OCT

Calibration

Circuitry

VCCIO

RUP

RDN

External

Calibration

Resistor

External

Calibration

Resistor

GND

EP3C80 Datasheet(PDF) 108 Page - Altera Corporation