ADAU 1442 PCM Inputs

Hello,

There might be a confusion in nomenclature here. I2S (inter-IC sound) is an audio interface that transfers data encoded in linear PCM (pulse code modulation) format. So, I2S actually is a kind of PCM.

The ADAU144x devices allow you to set the number of data bits in the word, the number of channels in the frame, and where the MSB (most significant bit) starts in relation to the frame start (delay by 0, 1, or 8). You can also set the frame clock waveform type, and the clock polarity for the frame clock and the bit clock.

Hello,

I am bringing up my new project and need help to understand "delayed by 8"

I have connected the serial data input port 5 of ADAU1442 to the data serial out of audio ADC (PCM4202). The sample rate of both are 48KHz, I2S ( Negative LRCK and Negative BCLK polarities) . DSP is master and ADC is set to slave. I made a very simple pass through DSP layout by sigma studio and loaded it in the DSP. In Sigma studio,The input level detector won't detect any audio activity when the port is set to I2S delayed by 1. The level detector detects the audio input when I change the port setting to "delayed by 8". why?

delayed by 8 is right justified or is still I2S format???

I used Prism dScope to verify the I2S bus. I2S data is valid and the sound analyzer locks to my board clock, both channels have valid data. I don't have to change the settings to "delayed by x" to lock the Prism to my board.

I have other Serial data inputs ( port 1 & port 2) to ADAU1442 , the level detector detects the audio data with I2S (delayed by one) without any issue.

I interfaced PCM4202 to SRC4382 on my previous design and the format was I2S (delayed by one).

Thanks,

Semi

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