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AD9255 PN9 and PN23 seed values

Question asked by antgol on Oct 16, 2015
Latest reply on Oct 17, 2015 by antgol

Hi,

 

I'm using AD9255 and try to validate digital interface with FPGA. So I'm checking different Output Test Modes. Positive and negative FS seems ok, alternating checkerboard seems ok, but PN sequences make me confused. PN9 is repeatable, is always the same after reset, but it is not as I expect. So I wonder about the seed value. In 9255 datasheet nothing is said about the seed, in AN877 Application Note the seed 0x092 is mentioned for all devices. But e.g. for AD9653 the seed value is all 1s. So what is correct for AD9255? And what 3 first numbers after reset should I get in 2-s complement mode (for seed 0x092 values should be x496, xFC9, xA99, correct?)? I wonder why AD does not make a simple counter as one of the test modes, it would be so much more convenient...


Thank You

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