Agilex™ 5 ES Device Errata and User Guidelines

ID 825514
Date 12/09/2024
Public
Document Table of Contents

2.2.18. HPS I3C0 and I3C1 SDA/SCL pin does not comply with High-Z bus condition

Description

The I3C master circuit does not support dynamic pull-up as specified by the I3C specification. Currently, the implementation of the SCL/SDA pins driver uses HPS IO with an internal weak pull-up resistor of 20 kOhm and static 1 K pull-up is implemented on the development kit. The constant pull-up with 1 kOhm on the SDA/SCL pins prevents the dynamic switching between Open-Drain, High-Z, and Push-Pull conditions from functioning correctly for I3C, leading to non-compliance with I3C electrical specifications. This could result in various compatibility issues with I3C devices related to the following points:

  • I3C0 does not support IBI
  • I3C1 does not support IBI, secondary master

In this configuration of the pull-up:

  • Base functionality for I3C slave and I2C slave devices were validated (dynamic and static addresses)
  • I2C data rates are supported (FM, FM+)
  • I3C data rates are supported up to 12.5 MHz

Workaround

No workaround for HPS IO. Alternatively, you can route the I3C to HVIO through FPGA fabric.

Note: The production device HPS I3C includes an additional signal called PULLUP_EN for SDA. This pin serves the purpose of dynamic switching to Open-Drain mode and should be connected to a strong pull-up resistor. This resistor is distinct from the static weak pull-up resistors on the SDA bus lines. Review your board design and make any necessary changes.