pullup in Xilinx ISE 10.1

[Jon Elson]

I tried building a small project in ISE 10.1 using the
CoolRunner II CPLD XC2C128 and ran into a problem with pullups.
I defined a few inputs with pullup in the UCF file, and
the mapper complained about a conflict between keeper
and pullup on the same pin. I had to set unused pins
and inputs to default to pullup to get rid of the error,
otherwise I just got the keeper and no pullup. it seems
the ucf command for pullup isn't being obeyed. Is the
CoolRunner II only able to have pullups if they are used
on all (input) pins?

Thanks,

Jon

 

[Jon Elson]

Jon Elson wrote:

I tried building a small project in ISE 10.1 using the
CoolRunner II CPLD XC2C128 and ran into a problem with pullups.
I defined a few inputs with pullup in the UCF file, and
the mapper complained about a conflict between keeper
and pullup on the same pin. I had to set unused pins
and inputs to default to pullup to get rid of the error,
otherwise I just got the keeper and no pullup. it seems
the ucf command for pullup isn't being obeyed. Is the
CoolRunner II only able to have pullups if they are used
on all (input) pins?
Yup, that's it, now I remember seeing that in the data sheet, not

very boldly described, either. The selection of keeper or
pullup/pulldown is a GLOBAL option for all inputs.
Well, at least what I saw was consistent with the docs.

Jon

 

[Gabor]

On 3/24/2013 12:50 PM, Jon Elson wrote:

Jon Elson wrote:

I tried building a small project in ISE 10.1 using the
CoolRunner II CPLD XC2C128 and ran into a problem with pullups.
I defined a few inputs with pullup in the UCF file, and
the mapper complained about a conflict between keeper
and pullup on the same pin. I had to set unused pins
and inputs to default to pullup to get rid of the error,
otherwise I just got the keeper and no pullup. it seems
the ucf command for pullup isn't being obeyed. Is the
CoolRunner II only able to have pullups if they are used
on all (input) pins?
Yup, that's it, now I remember seeing that in the data sheet, not
very boldly described, either. The selection of keeper or
pullup/pulldown is a GLOBAL option for all inputs.
Well, at least what I saw was consistent with the docs.

Jon

You can select whether you have any termination on a pin-by-pin basis,

but for those pins that have termination, it must be the same. So
in effect pullup vs. keeper vs. pulldown is global, but any of these
vs. tristate is available on a pin-by-pin basis.

-- Gabor