EP2AGX95EF29C6N Datasheet, PDF (186/380 Pages) Altera Corporation – Device Interfaces and Integration

6–22
Chapter 6: I/O Features in Arria II Devices
OCT Support
You can enable the left-shift series termination control feature in the ALTIOBUF
megafunction in the Quartus II software. The Quartus II software only allows
left-shift series termination control for 25- calibrated R_S OCT with 50- external
reference resistors connected to the RUP and RDN pins. You can only use left-shift series
termination control for the I/O standards that support 25- calibrated R_S OCT.
1 This feature is automatically enabled if you are using a bidirectional I/O with 25-
calibrated R_S OCT and 50- R_T OCT.
f For more information about how to enable the left-shift series termination feature in
the ALTIOBUF megafunction, refer to the I/O Buffer (ALTIOBUF) Megafunction User
Guide.
Expanded R_S OCT with Calibration for Arria II GZ Devices
OCT calibration circuits always adjust R_S OCT to match the external resistors
connected to the RUP and RDN pin; however, it is possible to achieve R_S OCT values
other than the 25- and 50- resistors. Theoretically, if you need a different R_S OCT
value, you can change the resistance connected to the RUP and RDN pins accordingly.
Practically, the R_S OCT range that Arria II GZ devices support is limited because of
output buffer size and granularity limitations.
The Quartus II software only allows discrete R_S OCT calibration settings of 25, 40, 50,
and 60  . You can select the closest discrete value of R_S OCT with calibration settings
in the Quartus II software to your system to achieve the closest timing. For example, if
you are using 20- R_S OCT with calibration in your system, you can select the 25-
R_S OCT with calibration setting in the Quartus II software to achieve the closest
timing.
Table 6–12 lists expanded R_S OCT with calibration supported in Arria II devices. Use
expanded R_S OCT with calibration of SSTL and HSTL for impedance matching to
improve signal integrity but do not use it to meet the JEDEC standard.
Table 6–12. Selectable I/O Standards with Expanded R_S OCT with Calibration Range for Arria II GZ
Devices
I/O Standard
3.3-V LVTTL/LVCMOS
2.5-V LVTTL/LVCMOS
1.8-V LVTTL/LVCMOS
1.5-V LVTTL/LVCMOS
1.2-V LVTTL/LVCMOS
SSTL-2
SSTL-18
SSTL-15
HSTL-18
HSTL-15
HSTL-12
Expanded R_S OCT Range
Row I/O ()
Column I/O ()
20–60
20–60
20–60
20–60
20–60
20–60
40–60
20–60
40–60
20–60
20–60
20–60
20–60
20–60
40–60
20–60
20–60
20–60
40–60
20–60
40–60
20–60
Arria II Device Handbook Volume 1: Device Interfaces and Integration
December 2011 Altera Corporation