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Explorer
Explorer
942 Views
Registered: ‎07-18-2011

XAPP1313 SPI flash configuration at 1.35V on bank 14 for Artix-7?

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I have an Artix-7 design, using the XC7A100T-2FGG484I, that has a 64-bit DDR3 interface to achieve the MIG bandwidth I require, so I have to run banks 14,15, and 16 at  1.35V to interface to the four x16 SDRAMs.   Unfortunately, bank 14 also has to be connected to the SPI flash for master SPI programming, and I am using a S25FL256SAGNFI001 QSPI flash powered from 3.3V, so it isn't compatible with the 1.35V I/O.

 

I found XAPP1313 that details using a bidirectional, auto-sensing level translator to allow a Spartan-7 to run bank 14 at 1.35V and interface a higher voltage SPI flash.   I am curious why the app note only mentions Spartan-7.  Is there was any reason it might not also work for an Artix-7?

 

In addition, the app note states that 2k pullup resistors are required for the FCS_B pin on the 1.35V FPGA side, and also on DQ2/W# and DQ3/HOLD# on the 1.8V SPI flash side.    Nearly all of the fast auto-sensing bidirectional level translators I can find state that either no pullups can be used, or they require a minimum resistance of 20k or 50k for any pullups attached to the I/O pins.   Do these pullups have to be 2K, or can 20k or 50k be used?  

 

The only parts I have found that allow lower value pullups are some Pericom parts that have internal 10k pullups, such as the P14ULS5V202, but they are limited to max 20Mb/s data rates, which I suppose I can live with by slowing down the configuration clock.   They do have the P14ULS3V302 device that runs at a blazing 140Mb/s, but they don't mention any pullup restrictions, so I am not sure if it will work.

 

 

 

 

 

 

 

 

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Community Manager
Community Manager
1,145 Views
Registered: ‎08-30-2011

Re: XAPP1313 SPI flash configuration at 1.35V on bank 14 for Artix-7?

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Hi Reaiken,

 

I think the reason that the APP note only mention the Spartan7 is that hardware verification only performed on Spartan7 platform. A7 should also be able to be used with this way but no hardware platform available for verification.

 

 

 

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Explorer
Explorer
895 Views
Registered: ‎07-18-2011

Re: XAPP1313 SPI flash configuration at 1.35V on bank 14 for Artix-7?

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In further reading of the datasheet, I found the TXS0108E level translator recommended in note 1, so I will use this one, as it obviously worked with pullup resistors for the app note design.

 

I also was able to find a 1.8V SPI flash from the 7-series recommended compatible parts that was in stock, the Macronix MX25U25635FZ2I-10G, so I can run bank 0 off of 1.8V as recommended in the app notes.

 

This leaves only one remaining question - will this circuit work with an Artix-7?  I was under the impression that the Spartan-7 was essentially the same device as an Artix-7 minus the GTP transceivers.   It just seems odd that the app note would only mention the Spartan-7 device.

 

 

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Community Manager
Community Manager
1,146 Views
Registered: ‎08-30-2011

Re: XAPP1313 SPI flash configuration at 1.35V on bank 14 for Artix-7?

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Hi Reaiken,

 

I think the reason that the APP note only mention the Spartan7 is that hardware verification only performed on Spartan7 platform. A7 should also be able to be used with this way but no hardware platform available for verification.

 

 

 

-------------------------------------------------------------------------------------------------
Don’t forget to reply, kudo, and accept as solution.
-------------------------------------------------------------------------------------------------
如果提供的信息能解决您的问题,请标记为“接受为解决方案”。
如果您认为帖子有帮助,请点击“奖励”。谢谢!
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Visitor mario.ploner
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Registered: ‎11-03-2015

Re: XAPP1313 SPI flash configuration at 1.35V on bank 14 for Artix-7?

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Hi reaiken,

does your design works with the TXS0108E ?

which pull-up values are you using (2k ?)

Mario

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