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8,879 Views
Registered: ‎06-12-2014

IBIS model Virtex7

Dear everybody,

 

I have a question about the available models on the ibis file of the Virtex7. Indeed, I have not found a response on the document, thus I need help.

 

I would like to know what is the difference between models "SSTL18_I_S" and SST18_II_S" for example ? It seems to be 2 types of models, type I and type II but I don't find any details about that...

 

Please if you have any issue...

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Moderator
Moderator
8,877 Views
Registered: ‎02-16-2010

Please refer to ug471 (7-series selectio user guide), page 74 to 84. You can find details about all different types of SSTL standards.
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Xilinx Employee
Xilinx Employee
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Registered: ‎08-01-2012

The termination style (class-I & class-II) required is based on the DDR memory application.

 

SSTL18 is defined by the JEDEC standard JESD8-15, and is used for DDR2 SDRAM memory interfaces.

 

The class-I driver can only be used in unidirectional topologies (no bidirectional support).

 

The class-II driver can be used for both for bidirectional and unidirectional signaling. For some topologies (such as short, point-to-point interfaces), the class-I driver can result in reduced overshoot and better signal integrity.

 

 

 

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