Analog Devices AD1847/ADSP-2181 Daisy Chain Tips Application Note

About this manual

This Engineer's Note addresses issues that may arise when interfacing multiple AD1847 SoundPort Codecs to an ADSP-21xx DSP while operating in '1-wire' mode. It focuses on the proper sequence for changing the crystal input 'on the fly', specifically when using a master and slave configuration.

What's inside

• Overview
• Problem Description
• Initialization Sequence
• Analog Loopback Test
• Crystal and Sample Rate Changes
• Master vs Slave Clocking

Frequently asked questions

Why does the master provide a 12.288 MHz clock on the clockout pin when it is in XTAL1 mode?

The master codec divides the XTAL1 input by 2 before using it (12.288mhz). Slave codecs use the XTAL2 input only and do not do a divide by two.

Can you send an additional config command to the 1847 during the time window after the XTAL is changed?

No, we would not recommend that. If you are changing the configuration, you should put the part into MCE.