6–10
Chapter 6: I/O Features in the Cyclone III Device Family
OCT Support
shows the external calibration resistors setup on the
RUP
and
RDN
pins and
the associated OCT calibration circuitry.
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
V
CCIO
External
Calibration
Resistor
RUP
OCT
Calibration
Circuitry
V
CCIO
RDN
External
Calibration
Resistor
GND
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 (R
S
= 50
)
for
SSTL-2
and
SSTL-18.
Cyclone III Device Handbook
Volume 1
July 2012 Altera Corporation
ALTERA [ ALTERA CORPORATION ]
