Hi, 

I started using the Multiply-and-Accumulate module of the PRU of my 
Beaglebone Black to construct a real-time digital filter. But as soon as I 
insert an instruction of the type, with any data or any of the MAC 
registers (r25-r29) in the code, I induce some non-negligeable latency. 
    MOV r25,0x00000000
    XOUT 0,r25,1

I would estimate that the XOUT or XIN instructions cost about 5 
microseconds, that is something near 1024 PRU clock cycles. I have observed 
other awkward behaviour of the Multiplier module, for example it only 
properly multiplied the values in registers r28 and r29 when I did a XOUT 
0,r28,8 instruction before reading the result. Does someone have experience 
with this module? Is it possible that I am using it wrong, that it has to 
be activated properly before being usable, or that the hardware is not 
working correctly? 

Thanks for any help!
Lenny

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