DSP Readback module create "click" noise

Hi , 

      We are using ADSP 21489 . In order to minimize the latency ( measured  between Analog In and  Analog Out ).  The processor buffer size was tried to reduce from 64 -> 32 -> 24 ...etc   When

the dsp readback module is working ( e.g. read 50 times per second ) , it creates "click" noise from buffer size 32 or smaller.   The average MIPS of schematic at that moment is only around


Here below are my questions : 

1. It seems that the Readback module will use a lot of MIPS, it is not very suitable to be used. We checked that the schematic itself can run properly ( no readback module active ) and consume 300MHz. Once readback is activated ( e.g. read 50 times per second ) ,  there is "click" noise even schematic is only used 230MHz.  It is not very really make sense.   Is that normal ? 

2. Is there any way instead of using readback module , it can read signal level in more efficient way ?