Chapter 6: I/O Features in the Cyclone III Device Family
6–7
OCT Support
f
For more information about the Cyclone III device family high-speed differential
interface support, refer to the High-Speed Differential Interfaces in the Cyclone III Device
Family chapter.
OCT Support
The Cyclone III device family features OCT to provide output impedance matching
and termination capabilities. OCT helps to prevent reflections and maintain signal
integrity while minimizing the need for external resistors in high pin-count ball grid
array (BGA) packages.
The Cyclone III device family provides output driver on-chip impedance matching
and on-chip series termination for single-ended outputs and bidirectional pins. For
bidirectional pins, OCT is active only for output.
1
When using on-chip series termination, programmable current strength is not
available.
There are two ways to implement OCT in the Cyclone III device family:
■
OCT with calibration
■
OCT without calibration
Table 6–3 lists the I/O standards that support output impedance matching and series
termination.
Table 6–3. Selectable I/O Drivers for On-Chip Series Termination with and Without Calibration Setting
On-Chip Series Termination with Calibration On-Chip Series Termination Without Calibration
Setting, in ohms ()
Setting, in ohms ()
I/O Standard
Row I/O
Column I/O
50, 25
50, 25
50, 25
50, 25
50, 25
50
Row I/O
Column I/O
50, 25
50, 25
50, 25
50, 25
50, 25
50
3.0-V LVTTL/LVCMOS
2.5-V LVTTL/LVCMOS
1.8-V LVTTL/LVCMOS
1.5-V LVCMOS
50, 25
50, 25
50, 25
50, 25
50
50, 25
50, 25
50, 25
50, 25
50
1.2-V LVCMOS
SSTL-2 Class I
50
50
SSTL-2 Class II
25
25
25
25
SSTL-18 Class I
SSTL-18 Class II
HSTL-18 Class I
HSTL-18 Class II
HSTL-15 Class I
HSTL-15 Class II
HSTL-12 Class I
HSTL-12 Class II
50
50
50
50
25
25
25
25
50
50
50
50
25
25
25
25
50
50
50
50
25
25
25
25
50
50
50
50
—
25
—
25
July 2012 Altera Corporation
Cyclone III Device Handbook
Volume 1
ALTERA [ ALTERA CORPORATION ]
