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AD9249  testmode PN-9

Question asked by 肖大屌 on Feb 3, 2016
Latest reply on Feb 18, 2016 by DougI

In ad9249 datasheet, The PN sequence short pattern produces a pseudorandom bit sequence that repeats itself every 511 bits(ITU 0.150  X^9+X^5+1).The seed value is all 1s. The output is a parallel representation of the serial PN9 sequence in MSB-first format.The first output word is the first 14 bits of the PN9 sequence in MSB aligned form.

       Sequence                  Initial value             Next three output samples (MSB first) twos complement

PN sequence short              0X1FE0                     0X1DF1 , 0X3CC8,  0X294E


I  don't undersand that why the initial value is 0X1FE0 since that the seed value is all 1s. And if I take the first 9 bits of the initial value into X^9+X^5+1 , the calculation results don't agree with the next three output samples.

I want to konw why  the initial value is 0X1FE0 and how to calcaulate the next output. thanks!