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ADAU1701:  How many instructions?

Question asked by KJBob on Aug 3, 2018



   It's well known that some of the ADAU1701's 1024 instructions (at 48K sample rate) are needed for what's generally described as "overhead."  Is there a better-defined answer for exactly how many must be left on the table?  For example, a bug fix has resulted in one of the DSPs in the mixer we make to run 1015 instructions.  The code compiles and the prototype I tried it in works fine.  Is there any downside in running this close to the edge?  I once thought that if the exported TxBuffer file shows a few NOPs (code 0x00, 0x00, 0x00, 0x00, 0x01), it's good to go.  Yet in this case the 9 NOPs I see adds up to 1024 -- so apparently this doesn't reflect the overhead either.  It would be good to know what's involved with this "overhead."


Edit:  I just reworked some logic in an attempt to shrink the project.  What I had thought was quite clever saved me exactly one instruction.  It's down to 1014 now.


   Thanks, Bob