[LatticeECP3]: How does the word alignment signal work in HDMI (High-Definition Multimedia Interface) in HDMI/DVI Interface Reference Design (RD1097)?
The word alignment function in PCS is use to catch the 4 dedicated commas. The HDMI data codec format is not the real G8B10B, one internal word alignment module was used to make the function more robust.
With the improvement of the internal word alignment module, the word_alignment function of PCS is not necessary. "word_align_en_chx" is tied to high. The real word alignment function is implemented in the internal modules. The internal word alignment module will check the word-alignment status periodically and might trigger one internal reset when the related errors have been detected. The signal "rx_status" of "hdmi_rx" module could show the current status.
After reset (or resync is triggered), if 8 consecutive special bytes (in blank period which is used to do word alignment) are detected, the signal word_aligned will be asserted, it will not be de-asserted until reset or resync is issued.
If 8 consecutive special bytes cannot be detected in 2^12 bytes, the signal word_align_err will be asserted. This will trigger the internal reset state machine rlos_reset, but the reset will be asserted after 2^23 clock cycles. And this will reset both the Serializer/Deserializer (SERDES) and HDMI receiver.