Intel® Stratix® 10 General Purpose I/O User Guide

ID 683518
Date 7/07/2021
Public
Document Table of Contents

3.3. Guideline: Voltage-Referenced and Non-Voltage Referenced I/O Standards

Each I/O bank can simultaneously support multiple I/O standards. Follow these guidelines if you use both non-voltage-referenced and voltage-referenced I/O standards in an I/O bank.

Non-Voltage-Referenced I/O Standards

An I/O bank can simultaneously support any number of input signals with different I/O standard assignments if the I/O standards support the VCCIO level of the I/O bank.

For output signals, a single I/O bank supports non-voltage-referenced output signals that drive at the same voltage as VCCIO. Because an I/O bank can only have one VCCIO value, it can only drive out the value for non-voltage-referenced signals.

Voltage-Referenced I/O Standards

To accommodate voltage-referenced I/O standards:

  • Each Intel® Stratix® 10 FPGA I/O bank contains a dedicated VREF pin.
  • Each bank can have only a single VCCIO voltage level and a single voltage reference (VREF) level.

The voltage-referenced input buffer is powered by VCCPT. Therefore, an I/O bank featuring single-ended or differential standards can support different voltage-referenced standards under the following conditions:

  • The VREF are the same levels.
  • On-chip parallel termination (RT OCT) is disabled.

If you enable RT OCT, the voltage for the input standard and the VCCIO of the bank must match.

This feature allows you to place voltage-referenced input signals in an I/O bank with a VCCIO of 1.8 V or below. For example, you can place HSTL-15 input pins in an I/O bank with 1.8 V VCCIO. However, the voltage-referenced input with RT OCT enabled requires the VCCIO of the I/O bank to match the voltage of the input standard. RT OCT cannot be supported for the HSTL-15 I/O standard when VCCIO is 1.8 V.

Voltage-referenced bidirectional and output signals must be the same as the VCCIO voltage of the I/O bank. For example, you can place only SSTL-18 output pins in an I/O bank with a 1.8 V VCCIO.

Mixing Voltage-Referenced and Non-Voltage Referenced I/O Standards

An I/O bank can support voltage-referenced and non-voltage-referenced pins by applying each of the rule sets individually.

Examples:

  • An I/O bank can support SSTL-18 inputs and outputs, and 1.8 V inputs and outputs with a 1.8 V VCCIO and a 0.9 V VREF.
  • An I/O bank can support 1.5 V standards, 1.8 V inputs (but not outputs), and 1.5 V HSTL I/O standards with a 1.5 V VCCIO and 0.75 V VREF.

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