EP2AGX95EF29C6N Datasheet, PDF (188/380 Pages) Altera Corporation – Device Interfaces and Integration

6–24
Chapter 6: I/O Features in Arria II Devices
OCT Support
The R_T OCT calibration circuit compares the total impedance of the I/O buffer to the
external 50- ± 1% resistors connected to the RUP and RDN pins and dynamically
enables or disables the transistors until they match. Calibration occurs at the end of
device configuration. When the calibration circuit finds the correct impedance, it
powers down and stops changing the characteristics of the drivers. Table 6–13 lists the
I/O standards that support R_T OCT with calibration.
Table 6–13. Selectable I/O Standards with R_T OCT with Calibration for Arria II GZ Devices
I/O Standard
R_T OCT Setting
(Column I/O) ()
R_T OCT Setting
(Row I/O) ()
SSTL-2 Class I, II
50
50
SSTL-18 Class I, II
50
50
SSTL-15 Class I, II
50
50
HSTL-18 Class I, II
50
50
HSTL-15 Class I, II
50
50
HSTL-12 Class I, II
50
50
Differential SSTL-2 Class I, II
50
50
Differential SSTL-18 Class I, II
50
50
Differential SSTL-15 Class I, II
50
50
Differential HSTL-18 Class I, II
50
50
Differential HSTL-15 Class I, II
50
50
Differential HSTL-12 Class I, II
50
50
Dynamic R_S and R_T OCT for Single-Ended I/O Standard for Arria II GZ Devices
Arria II GZ devices support on and off dynamic termination, both series and parallel,
for a bidirectional I/O in all I/O banks. Figure 6–9 shows the termination schemes
supported in Arria II GZ devices. Dynamic parallel termination is enabled only when
the bidirectional I/O acts as a receiver and is disabled when it acts as a driver.
Similarly, dynamic series termination is enabled only when the bidirectional I/O acts
as a driver and is disabled when it acts as a receiver. This feature is useful for
terminating any high-performance bidirectional path because signal integrity is
optimized depending on the direction of the data.
Using dynamic OCT helps save power because device termination is internal instead
of external. Termination only switches on during input operation, thus drawing less
static power.
Arria II Device Handbook Volume 1: Device Interfaces and Integration
December 2011 Altera Corporation