Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

unbonded output ports

Status
Not open for further replies.

shaiko

Advanced Member level 5
Joined
Aug 20, 2011
Messages
2,644
Helped
303
Reputation
608
Reaction score
297
Trophy points
1,363
Activity points
18,300
What is the state of output pins that aren't bond in the FPGA UCF file ?

some_output <= '1' ; -- "some_output" is defined as an output port in the top entity but not defined in the UCF file

What will happen ?
 
Last edited:

gongdori

Full Member level 2
Joined
Mar 7, 2012
Messages
133
Helped
21
Reputation
42
Reaction score
19
Trophy points
1,298
Activity points
2,035
I think the tool picks up a pin and assign the output signal to it (the pin for the best timing, I guess?).
 
  • Like
Reactions: shaiko

    shaiko

    Points: 2
    Helpful Answer Positive Rating

permute

Advanced Member level 3
Joined
Jul 16, 2010
Messages
923
Helped
295
Reputation
590
Reaction score
268
Trophy points
1,343
Activity points
8,543
yes, the tools will pick a spot at random. I really don't know who thought this was a good default, but it's what happens.
 
  • Like
Reactions: shaiko

    shaiko

    Points: 2
    Helpful Answer Positive Rating

joelby

Full Member level 4
Joined
Jun 6, 2011
Messages
196
Helped
66
Reputation
130
Reaction score
64
Trophy points
1,308
Activity points
2,644
I'm not sure about the exact algorithm it applies, but it can be useful if you're planning to design a circuit board and want to let the tools fit pins in optimal locations, which can help when there are slightly non-obvious constraints (such as half bank clocking regions, I/O buffer type and voltage restrictions, etc.). There's nothing worse than building a board and finding out too late that your design can't fit the pin placement you picked.
 
  • Like
Reactions: shaiko

    shaiko

    Points: 2
    Helpful Answer Positive Rating

samuraign

Full Member level 2
Joined
May 18, 2006
Messages
127
Helped
12
Reputation
24
Reaction score
5
Trophy points
1,298
Activity points
1,881
You have option while generting the bitfile to decide about unconnected pins either to pull-up/pull-down or floating
 
  • Like
Reactions: shaiko

    shaiko

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top