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validating eye mask in differential signals.

Question asked by 9dc1212f-cb89-8a24-0100-014e727abccf on Jun 27, 2016

There is slight confusion while viewing signal quality for ddr4 single ended as well as differential signals, In datasheet it is mentioned:-

VIH(ac)-min=750 mV

VIH(dc)_min=700 mV

VIH(dc)_max=500 mV

VIH(ac)_max=450 mV


whereas for differential signals it is mentioned as

VIH(ac)_diff_min  = 300mV

VIH(dc)_diff_min = 200 mV

VIH(dc)_diff_max = 200 mV

VIH(ac)_diff_max = -300 mV


so i should consider eye mask from 300 to -300 mV for differential signals or add 600 mV in it to get eye mask from 900 to 300 mV, signals DQS_c and DQS_t will never come to -300 mV.


WHAT IS THE INTERPRETATION FROM -300 TO 300 mV, Does this is simply specifying the voltage swing or voltage levels ?