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AR# 9425

Virtex/E - Banking Rule Differences, and mixing different I/O standards, Vref, Vcco

Description

How do the banking rules differ between Virtex and Virtex-E? 

 

Can I use inputs from one standard and outputs from a different standard in the same bank?

Solution

Differences: 

In Virtex, the input buffers are powered by Vccint, and output buffers are powered by Vcco. In Virtex-E the LVTLL, LVCMOS2, and PCI input buffers are powered by Vcco. This gives a more strict banking rule in Virtex-E.  

 

Virtex: 

For Virtex, the solution is explained clearly in the Virtex Databook. Vrefs are strictly referenced voltages for an input standard, and Vccos are the voltages for an output standard. The two are mutually exclusive.  

 

Thus: 

1. For input standards to be mixed, the two must have the same Vrefs, or at least one of them must be an "N/A." If the standard in question is to be used only for inputs, only the Vref's need to be compared. 

 

2. For output standards to be mixed, the two must have the same Vccos, or at least one of them must be an "N/A." If the standard in questions is to be used only for outputs, only the Vcco's need to be compared. 

 

 

Virtex-E:  

For Virtex-E the banking rules have changed: Outputs depend only on Vcco. However, inputs depend on Vcco and Vref. They are no longer mutually exclusive. 

 

1. For an input standard to be mixed, the two must have the same Vrefs and the same Vccos. "N/A"s can be used as wildcards and can be mixed with any standard. If the standard in question is to be used only for inputs, both the Vcco's and Vref's must 

be compared. 

 

2. For an output standard to be mixed, the rule is the same as in Virtex. The two must have the same Vccos, or at least one of them must be an "N/A." If the standard in question is to be used only for outputs, only the Vcco's must be compared.

AR# 9425
Date Created 08/21/2007
Last Updated 05/14/2014
Status Archive
Type General Article