10 cycles is for redundant initialization and checking, previously it was only 1 time. I did it for experiment and left for now. I don't know anything about diagnostic mode, because data sheet has no proper information, so that is why I don't use diagnostic mode and leave ~TEST in high state. SO terminal immediately repeats state of SI, I think it is directly multiplexed without any logic involved

I tried to find more information about diagnostic mode, but without success. My chip is without 'Z'. Only 'AB', but it does not matter I think. IMHO - datasheet for HIP9011 is full of shit.