HDMI Intel® Arria 10 FPGA IP Design Example User Guide

ID 683156
Date 11/12/2021
Public

A newer version of this document is available. Customers should click here to go to the newest version.

Document Table of Contents

4.2. Nios II Processor Software Flow

The Nios II software flowchart includes the HDCP authentication controls over HDMI application.

Figure 30. Nios II Processor Software Flowchart
  1. The Nios II software initializes and resets the HDMI TX PLL, TX transceiver PHY, I2C master and the external TI retimer.
  2. The Nios II software polls periodic rate detection valid signal from RX rate detection circuit to determine whether video resolution has changed and if TX reconfiguration is required. The software also polls the TX hot-plug detect signal to determine whether a TX hot-plug event has occurred.
  3. When a valid signal received from RX rate detection circuit, the Nios II software reads the SCDC and clock depth values from the HDMI RX and retrieves the clock frequency band based on the detected rate to determine whether HDMI TX PLL and transceiver PHY reconfiguration are required. If TX reconfiguration is required, the Nios II software commands the I2C master to send the SCDC value over to external RX. It then commands to reconfigure the HDMI TX PLL and TX transceiver PHY, followed by device recalibration, and reset sequence. If the rate does not change, neither TX reconfiguration nor HDCP re-authentication is required.
  4. When a TX hot-plug event has occurred, the Nios II software commands the I2C master to send the SCDC value over to external RX, and then read EDID from RX and update the internal EDID RAM. The software then propagates the EDID information to the upstream.
  5. The Nios II software starts the HDCP activity by commanding the I2C master to read offset 0x50 from external RX to detect if the downstream is HDCP-capable, or otherwise:
    • If the returned HDCP2Version value is 1, the downstream is HDCP2x-capable.
    • If the returned value of the entire 0x50 reads are 0’s, the downstream is HDCP1x-capable.
    • If the returned value of the entire 0x50 reads are 1’s, the downstream is either not HDCP-capable or inactive.
    • If the downstream is previously not HDCP-capable or inactive but is currently HDCP-capable, the software sets the REPEATER bit of the repeater upstream (RX) to 1 to indicate the RX is now a repeater.
    • If the downstream is previously HDCP-capable but is currently not HDCP-capable or inactive, the software sets the REPEATER bit of to 0 to indicate the RX is now an endpoint receiver.
  6. The software initiates the HDCP2x authentication protocol that includes RX certificate signature verification, master key exchange, locality check, session key exchange, pairing, authentication with repeaters such as topology information propagation.
  7. When in authenticated state, the Nios II software commands the I2C master to poll the RxStatus register from external RX, and if the software detects the REAUTH_REQ bit is set, it initiates re-authentication and disables TX encryption.
  8. When the downstream is a repeater and the READY bit of the RxStatus register is set to 1, this usually indicates the downstream topology has changed. So, the Nios II software commands the I2C master to read the ReceiverID_List from downstream and verify the list. If the list is valid and no topology error is detected, the software proceeds to the Content Stream Management module. Otherwise, it initiates re-authentication and disables TX encryption.
  9. The Nios II software prepares the ReceiverID_List and RxInfo values and then writes to the Avalon-MM Repeater Message port of the repeater upstream (RX). The RX then propagates the list to external TX (upstream).
  10. Authentication is complete at this point. The software enables TX encryption.
  11. The software initiates the HDCP1x authentication protocol that includes key exchange and authentication with repeaters.
  12. The Nios II software performs link integrity check by reading and comparing Ri’ and Ri from external RX (downstream) and HDCP1x TX respectively. If the values do not match, this indicates loss of synchronization and the software initiates re-authentication and disables TX encryption.
  13. If the downstream is a repeater and the READY bit of the Bcaps register is set to 1, this usually indicates that the downstream topology has changed. So, the Nios II software commands the I2C master to read the KSV list value from downstream and verify the list. If the list is valid and no topology error is detected, the software prepares the KSV list and Bstatus value and writes to the Avalon-MM Repeater Message port of the repeater upstream (RX). The RX then propagates the list to external TX (upstream). Otherwise, it initiates re-authentication and disables TX encryption.

Did you find the information on this page useful?

Characters remaining:

Feedback Message