I have a question about method of ZQ automatic pull-down calibration.
In ZQ automatic Pull-up calibration(section 126.96.36.199.1), it say that
"The MMDC drives zq_pu_pd_sel to "1"for indication of pull-up calibration"
From Figure 44-8 in Reference manual, It will connect between internal pull-up and external pull-down
register and calibrate a ZQPAD voltage to Vdd/2.
In ZQ automatic Pull-down calibration(188.8.131.52.2), it say that
"The MMDC drives zq_pu_pd_sel to "0" for indication of pull-down calibration"
In Figure 44-8, it seems that detach internal pull-up register and attach internal pull-down register
to external register.
It seems that both internal and external register are pull-down so ZQPAD keep GND level.
So we think that in pull-down zq calibration, internal pull-up and internal pull-down register
will attached to the comparator and detach external register.
Is it correct understanding?