Hi, thanks for the reply. I also noticed something else which might be related: To synchronize both PRU's, one sends every 250 clock cycles some data with a command XOUT 10,r13,4 which the other receives via XIN 10,r13,4.
This works well. If however i mismatch the registers, that is i combine XOUT 10,r13,4 on PRU0 with XIN 10,r14,4 on PRU1 th i still synchronize the two PRU's, even though I would expect both PRUs to simply stall here for 1024 cycles. Just thought this might be related to the other XIN/XOUT problems with the multiplier. 2014-04-16 18:36 GMT+02:00 Bas Laarhoven <s...@xs4all.nl>: > On 16-4-2014 18:31, Lenny wrote: > > 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 > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to beagleboard+unsubscr...@googlegroups.com. > > For more options, visit https://groups.google.com/d/optout. > > > Something is definitely wrong with your setup. I'm using the multiplier > for my BeBoPr stepper driver and IIRC the instruction takes only one PRU > cycle. > There's some overhead for set-up and to check the flags, but certainly > nothing like you're mentioning. > > -- Bas > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to a topic in the > Google Groups "BeagleBoard" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/beagleboard/lc_O_BHITjc/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > beagleboard+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
