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Observer reza1
Observer
522 Views
Registered: ‎07-10-2017

XA7Z030 PUDC shared with HP port IO

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Hello,

There are only some limited number of DIFF GPIO's available on XA7Z030FBG484 and I need to use ALL the HP DIFF pairs for high speed purposes which are SI critical.

IO_L3P_T_DQS_PUDC_B_34 is a multi function IO shared with PUDC and which needs to be pulled Hi or Low (before & during config) which will cause SI issues.

Wondering if there is any work around to take care of of PUDC internally or etc during and before configuration.

Thanks,

-Reza 

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Moderator
Moderator
474 Views
Registered: ‎09-18-2014

Re: XA7Z030 PUDC shared with HP port IO

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Reza1,

 

It sounds, it would be safer to take care of PUDC being shared with this IO and use it as a basic IO, taking care of the added pull up or pull down and to not use it as a SI critical line. 

-I think you have the right idea. High speed IOs are usually dedicated... adding additional or multi use functionalities always have some sort of drawback for such flexible features. 

 

Regards,

T

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Moderator
Moderator
495 Views
Registered: ‎09-18-2014

Re: XA7Z030 PUDC shared with HP port IO

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Reza1,

 

Well, for such function to be taken care of internally the FPGA would have to be programmed to do so but this occurs before any sort of configuration. PUDC_B is sampled at the positive edge of INIT. You may try checking the schematics of development kits out there from Xilinx, Digilent, Avenet, Digikey etc to see how they've worked with this caveat. This is why MIG doesn't allow you to use the byte group this pin is contained in standard pin allocation unless used through fixed pinout mode where you can use it as an address/control pin. 

 

 

Regards,

Tezz

Regards,

T

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Observer reza1
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Registered: ‎07-10-2017

Re: XA7Z030 PUDC shared with HP port IO

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Thanks for the clarification Tezz!

 

Actually I have seen in couple of EVAL BD schematics that they have ignored the PUDC functionality on this IO and have used this IO similar to other IO's as DIFF pair and etc (w/o any pull up or pull down as needed) But I don't want to do that.

 

It sounds, it would be safer to take care of PUDC being shared with this IO and use it as a basic IO, taking care of the added pull up or pull down and to not use it as a SI critical line. 

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Moderator
Moderator
475 Views
Registered: ‎09-18-2014

Re: XA7Z030 PUDC shared with HP port IO

Jump to solution

Reza1,

 

It sounds, it would be safer to take care of PUDC being shared with this IO and use it as a basic IO, taking care of the added pull up or pull down and to not use it as a SI critical line. 

-I think you have the right idea. High speed IOs are usually dedicated... adding additional or multi use functionalities always have some sort of drawback for such flexible features. 

 

Regards,

T

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