
Altera Corporation
4–25
June 2006
Stratix Device Handbook, Volume 2
Selectable I/O Standards in Stratix & Stratix GX Devices
An I/O bank featuring single-ended or differential standards can support
voltage-referenced standards as long as all voltage-referenced standards
use the same VREF setting. For example, although one I/O bank can
implement both SSTL-3 and SSTL-2 I/O standards, I/O pins using these
standards must be in different banks since they require different VREF
values
For voltage-referenced inputs, the receiver compares the input voltage to
the voltage reference and does not take into account the VCCIO setting.
Therefore, the VCCIO setting is irrelevant for voltage referenced inputs.
Voltage-referenced bidirectional and output signals must be the same as
the I/O bank’s VCCIO voltage. For example, although you can place an
SSTL-2 input pin in any I/O bank with a 1.25-V VREF level, you can only
place SSTL-2 output pins in an I/O bank with a 2.5-V VCCIO.
Mixing Voltage Referenced & Non-Voltage Referenced
Standards
Non-voltage referenced and voltage referenced pins can safely be mixed
in a bank by applying each of the rule-sets individually. For example, on
I/O bank can support SSTL-3 inputs and 1.8-V LVCMOS inputs and
outputs with a 1.8-V VCCIO and a 1.5-V VREF. Similarly, an I/O bank can
support 1.5-V LVCMOS, 3.3-V LVTTL (inputs, but not outputs), and
HSTL I/O standards with a 1.5-V VCCIO and 0.75-V VREF.
Guidelines” section. For details on how the Quartus II software supports