Intel® Agilex™ General-Purpose I/O and LVDS SERDES User Guide

ID 683780
Date 10/29/2021
Public

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3.1.1.1. RS OCT

Intel® Agilex™ devices support RS OCT with and without calibration for single-ended and voltage-referenced I/O standards.

OCT Scheme Description
RS without calibration
  • Only supported on output buffer.
  • Driver-impedance matching provides the I/O driver with a controlled output impedance that closely matches the impedance of the transmission line.
RS with calibration
  • The OCT calibration circuit uses the impedance of the external resistor that is connected to the RZQ pin as reference. The impedance of the I/O buffer is continuously altered until the target impedance is achieved during OCT calibration. The targeted impedance is achieved when the impedance of I/O buffer reaches a predetermined ratio to the reference resistance.
  • Calibration occurs at the end of device configuration. When the calibration circuit finds the correct impedance, the circuit powers down and stops changing the characteristics of the drivers.
  • You may trigger re-calibration during user-mode.
Figure 32. RS OCT Without CalibrationThis figure shows the RS as the intrinsic impedance of the output transistors.
Figure 33. RS OCT with CalibrationThis figure shows the RS as the intrinsic impedance of the output transistors.
Table 36.  Selectable I/O Standards for RS OCT for GPIO Banks
I/O Standard RS OCT without Calibration (Ω) RS OCT with Calibration (Ω)
1.2 V LVCMOS 34, 40 (Default) 34, 40
SSTL-12 34, 40 34, 40 (Default)
POD12 34, 40 34 (Default), 40
HSTL-12 34, 40 34, 40 (Default)
HSUL-12 34, 40 34, 40 (Default)
Differential SSTL-12 34, 40 34, 40 (Default)
Differential POD12 34, 40 34 (Default), 40
Differential HSTL-12 34, 40 34, 40 (Default)
Differential HSUL-12 34, 40 34, 40 (Default)

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