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Participant heiyux
Participant
9,424 Views
Registered: ‎02-19-2009

How do you deal with the IO standard incompatible problem when using SPI Flash in the configuration of Virtex-6

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hey, 

 

I'm about to use SPI flash to configure Virtex-6 SX315T. Since the Virtex-6 FPGA doesn't support 3.3V IO standard, there‘s a incompatible problem between SPI Flash and FPGA.

 

I found N25Q128 from Micron has a 1.8V version. But I wish to use the bank which contains the SPI function PINs as a 2.5V bank. The DC characteristic in N25Q128 is   (  VCC=1.8V  )

----------------------------------------------------------------------------------------

Parameter                                    |    MIN          |         MAX         |   Unit

----------------------------------------------------------------------------------------

Input low voltage (VIL)                |      –0.5       |     0.3VCC       |     V

Input high voltage  (VIH)             |     0.7VCC  |     VCC + 0.4  |     V

-----------------------------------------------------------------------------------------

Output low voltage (VOL)           |         –          |         0.4           |     V
Output high voltage (VOH)         | VCC - 0.2   |           –            |     V

-----------------------------------------------------------------------------------------

 

But the Virtex-6 LVCMOS25/LVDCI25 IO standard characteristic is  (VCCO=2.5V)

-------------------------------------------------------------------------------------------------------------------

VIL(min)  |  VIL(max)   |  VIH(min)  |     VIH(max)    |   VOL(max)  |  VOH(min)        | uint

-------------------------------------------------------------------------------------------------------------------

  –0.3       |       0.7        |       1.7        |   VCCO +0.3  |         0.4         |   VCCO – 0.4   |    V

------------------------------------------------------------------------------------------------------------------

 

I notice the SPI output high VCC-0.2=1.6 is not enough for FPGA input High min 1.7V.

 

then I compare the 3.3V version SPI’s DC characteristic with FPGA 2.5V IO standard. The DC characteristic of M25P128 is similar with N25Q128 1.8V,  just the VCC is 3.3V. We can see, if use 3.3V M25P, the FPGA output high min VCCO-0.2=2.1V is not enough for M25P input high min 0.7VCC=0.7*3.3=2.31V.

 

I don't want to use level shifter chip on this. I wonder if I could just use this two SPI chip in me design with directly connective, cause they are support by Virtex-6 as I know.

 

Thanks very much!

Any comment about SPI configure in Virtex-6  is appreciated!

 

Thank you!

 

 

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1 Solution

Accepted Solutions
Teacher eteam00
Teacher
10,943 Views
Registered: ‎07-21-2009

Numonyx flash interfaced to V-6

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1.  Consider that your V6 VCCIO supply (1.8 or 2.5V) has some tolerance on it.  Be sure to account for min/max supply voltage from the regulator.

 

2.  Consider using the 3V part and running it at (nominal) 2.8V VCC.  The part consumes 20mA, max, so a very tiny and inexpensive local regulator can supply the necessary power (within 1-2%).

 

-- Bob Elkind

SIGNATURE:
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6 Replies
Teacher eteam00
Teacher
10,944 Views
Registered: ‎07-21-2009

Numonyx flash interfaced to V-6

Jump to solution

1.  Consider that your V6 VCCIO supply (1.8 or 2.5V) has some tolerance on it.  Be sure to account for min/max supply voltage from the regulator.

 

2.  Consider using the 3V part and running it at (nominal) 2.8V VCC.  The part consumes 20mA, max, so a very tiny and inexpensive local regulator can supply the necessary power (within 1-2%).

 

-- Bob Elkind

SIGNATURE:
README for newbies is here: http://forums.xilinx.com/t5/New-Users-Forum/README-first-Help-for-new-users/td-p/219369

Summary:
1. Read the manual or user guide. Have you read the manual? Can you find the manual?
2. Search the forums (and search the web) for similar topics.
3. Do not post the same question on multiple forums.
4. Do not post a new topic or question on someone else's thread, start a new thread!
5. Students: Copying code is not the same as learning to design.
6 "It does not work" is not a question which can be answered. Provide useful details (with webpage, datasheet links, please).
7. You are not charged extra fees for comments in your code.
8. I am not paid for forum posts. If I write a good post, then I have been good for nothing.
Voyager
Voyager
9,406 Views
Registered: ‎10-01-2007

Re: How do you deal with the IO standard incompatible problem when using SPI Flash in the configuration of Virtex-6

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The Spansion S25FL-S family can support Vio of 2.5V (full range is 1.65V - 3.6V).

  http://www.spansion.com/Support/Datasheets/S25FL128S_256S_00.pdf

 

Bryan

Participant heiyux
Participant
9,392 Views
Registered: ‎02-19-2009

Re: Numonyx flash interfaced to V-6

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Thanks, Bob.

 

The method changing VCC voltage will be taken consideration. The 2.8V VCC will work.

 

Thanks very much!

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Participant heiyux
Participant
9,391 Views
Registered: ‎02-19-2009

Re: How do you deal with the IO standard incompatible problem when using SPI Flash in the configuration of Virtex-6

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Hey Bryan,

Thanks for advising. I checked the datasheet and this will be exact the chip I need. But I notice that the impact software in ISE 13.3 has still not support the S25FL-S family yet. Only S25FL-P is supported.

See http://www.xilinx.com/support/documentation/sw_manuals/xilinx13_3/pim_r_supported_spi_bpi_proms.htm

Can I select S25FL129P in impact when I use S25FL128S on board?
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Voyager
Voyager
9,369 Views
Registered: ‎10-01-2007

Re: How do you deal with the IO standard incompatible problem when using SPI Flash in the configuration of Virtex-6

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I suggest opening a case with Xilinx Support.  Perhaps they have Beta support for this device which is hidden.

 

Otherwise, it's not too difficult to adapt the PicoBlaze SPI Flash Programmer that Xilinx originally created for the Spartan-3E/A Starter Kits for SPI programming.

 

Bryan

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Participant heiyux
Participant
9,339 Views
Registered: ‎02-19-2009

Re: How do you deal with the IO standard incompatible problem when using SPI Flash in the configuration of Virtex-6

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Hi Bryan,

Thanks for replying!

I get an answer from Kyle in another topic. But thanks all the same. I'll take the lower VCCO in S25FL129P suggested by Bob for my design and take the S25FL128S as a test.

Thanks very much!

Regards,
Day
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