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Observer patrick.lewis
Observer
4,607 Views
Registered: ‎01-06-2011

Defualt IO states

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I am interested in the default state of Spartan 6 and Virtex 4 IO pins.

 

For start-up we can use HSWAPEN to enable pullups, but what about once a board is programmed and running. If a pin is not defined in the design, does the FPGA continue to use weak pull ups, or do the pins become tri-stated. Has this always been the case?

 

Thanks,

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Teacher eteam00
Teacher
5,895 Views
Registered: ‎07-21-2009

Setting default IO states for unused pins

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The default for unused pins is electrically equivalent to an input with a weak pulldown resistor.  Of course, there is no "input" function associated with unused pins.

 

See UG628, the BitGen chapter.

 

In the current version (12.4), the syntax is (page 249):

-g UnusedPin:{Pullup | Pulldown | Pullnone}

 

The default setting is

-g UnusedPin:Pulldown

 

If you want to change this setting from within ISE Project Navigator,  in the Processes pane

  • select the Generate Programming File process
  • right-click and select Process Properties from the pop-up context menu
  • in the Property display level drop-down list (at the bottom of the window), select Advanced
  • Select General Options in the left pane.
  • in the Other Bitgen Command Line Options entry row (right pane), enter the command line options (e.g. -g UnusedPins:Pullup)

-- 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.
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5. Students: Copying code is not the same as learning to design.
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4 Replies
Xilinx Employee
Xilinx Employee
4,600 Views
Registered: ‎08-25-2010

Re: Defualt IO states

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The HSWAPEN pin detemine whether the IOB has a pullup resistor during configruation and pre-configuration, after that,  unused IO state can be defined by the bitgen option:-g UnusedPin:

 

Thanks
Simon
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Teacher eteam00
Teacher
5,896 Views
Registered: ‎07-21-2009

Setting default IO states for unused pins

Jump to solution

The default for unused pins is electrically equivalent to an input with a weak pulldown resistor.  Of course, there is no "input" function associated with unused pins.

 

See UG628, the BitGen chapter.

 

In the current version (12.4), the syntax is (page 249):

-g UnusedPin:{Pullup | Pulldown | Pullnone}

 

The default setting is

-g UnusedPin:Pulldown

 

If you want to change this setting from within ISE Project Navigator,  in the Processes pane

  • select the Generate Programming File process
  • right-click and select Process Properties from the pop-up context menu
  • in the Property display level drop-down list (at the bottom of the window), select Advanced
  • Select General Options in the left pane.
  • in the Other Bitgen Command Line Options entry row (right pane), enter the command line options (e.g. -g UnusedPins:Pullup)

-- 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.

View solution in original post

Newbie joseg
Newbie
4,579 Views
Registered: ‎07-13-2011

Re: Defualt IO states

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Does the HSWAPEN pin have its own default state?  I have a layout where I forgot to connect the HSWAPEN pin on the Spartan 6--trying to use the SelectMAP configuration interface.

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Teacher eteam00
Teacher
4,574 Views
Registered: ‎07-21-2009

HSWAPEN default state before/during config

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Each FPGA family may be different on this question.

 

The information you seek is (for Spartan-6) in UG380, the Configuration User Guide.  HSWAPEN pin has an internal weak pullup (to VCCO_0) before and during configuration.  HSWAPEN is a user I/O after configuration.

 

- 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.
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