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AR# 69427

HDMI Transmitter (TX) Subsystem v2.0 (Rev. 5) - Why do I sometimes see DDC Transaction failures when the HDMI Sink requests clock stretching?

描述

Why do I sometimes see DDC Transaction failures when the HDMI Sink requests clock stretching?

解决方案

This is a known issue which occurs due to the way in which the DDC (I2C) clock stretching is implemented.

The HDMI Transmitter Subsystem has a timeout mechanism, which will time out if the slave holds the SCL low for more than 100ms (@100mhz CPU interface clock).

Once the timeout occurs, the state machine will go back to an idle state.

Therefore, after the slave release the SCL, it will start from an idle state which is then followed by the start condition etc., instead of resuming from the current state.

This can cause DDC transactions to fail.

This issue is resolved in the HDMI Transmitter Subsystem v3.0 in Vivado 2017.3 and later versions.

链接问答记录

主要问答记录

Answer Number 问答标题 问题版本 已解决问题的版本
65911 HDMI 1.4/2.0 发送器 (TX) 子系统 — Vivado 2015.4 工具及更新版本的版本说明和已知问题 N/A N/A
AR# 69427
日期 03/27/2018
状态 Active
Type 综合文章
IP
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