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Honored Contributor I
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JTAG and Config, Mutil Voltage, Multi Chip

Hello, 

 

I am using an Arria I dev kit to interface to a board that contains 3 FPGAs. The interface (HSMC) provides a JTAG connection plus a number of I/O that I will be using to do PS configuration for all 3 chips. The I/O standard from the HSMC is 2.5V but all the I/O standards on the 3 FPGAs are 3.3V. My questions are: 

 

1. Will the JTAG and Config work even if there is an I/O voltage mismatch? According to the specs, either side should tolerate the VIH levels. 

 

2. Do I need to use a level shifter like Altera does in other dev kits? 

 

3. Can I rely on controlling the drive strength of the I/O (used for PS config) coming from the dev kit to get better signal integrity or should I add series terminations? 

 

Thank you for you help!
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Honored Contributor I
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1 & 2 - What are the three FPGAs on the other board? More than likely, you'll be just fine between 2.5V and 3.3V. If you were going down to say 1.8V, you might have trouble. 

 

3 - I think you'll be fine with the on-chip current strength selection. This is a dev kit right? Adding a series resistor can actually hurt you if it's not in the right position (close to the driving pin). 

 

Jake
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Honored Contributor I
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Jake, thanks for the answer!  

 

Good point on 3. The termination should be at the source and I am quite far from it (in signal terms.) 

 

The other 3 FGPAs are Arrias (I) also.
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Honored Contributor I
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Yeah you'll be fine. See the section entitled "I/O Voltage Support in JTAG Chain" starting on page 13-17 of the Arria GX handbook: 

http://www.altera.com/literature/hb/agx/agx_52013.pdf 

 

Jake
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