MPC8315E - PCIe interface

[airazusta]

Hello,

I was wondering how I should disable/enable the SerDes PCIe interface of the MPC8315E via SW.  Would be enough to configure SDPD bit of SRDSCR0 register to '1' (Block power down) for disable it? 

And should I also make any change in HW? For example, following the application note AN3438, it says that SD_IMP_CAL_TX signal has to be connected to GND using a 100R precision resistor when the interface is used, but when not used it has to be connected to 1V. If I disable the PCIe interface via SW, can SD_IMP_CAL_TX signal still be connected to the 100R resistor?

Thanks in advance!

Regards,

Ane

[Bulat]

Yes, setting of SRDSCR0[24] bit is enough for powering down (disabling) entire SERDES from SW point of view.

Yes, if SERDES is not used, you can connect both SD_IMP_CAL_TX (and SD_IMP_CAL_RX) to 1V via 100 Ohm resistors.

Regards,

Bulat

[airazusta]

Thank you for answering Bulat!

And would it be ok if I leave both calibration signals connected to GND via 100 Ohm (or 200 Ohm) resistor when I power down the SERDES?

Regards,

Ane 

[Bulat · Accepted solution]

I believe it will be ok. Side effect is that grounded resistors could cause additional unnecessary power consumption.

Regards,

Bulat