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Comp.Arch.FPGA | How to create a LVPECL_25 output pair (Spartan3, ISE 9.1)

There are 3 messages in this thread.

You are currently looking at messages 0 to 3.

How to create a LVPECL_25 output pair (Spartan3, ISE 9.1) - Thomas Heller - 2010-07-21 15:23:00

I'm trying to create a LVPECL_25 differential
output on a Spartan 3
(XC3S200 device in PQ208 package).  I did this by selecting 'LVPECL_25'
in the I/O Standard column in PACE (assign package pins).

However, in 'Implement Design' I get the following error:

Process "Translate" completed successfully
Using target part "3s200pq208-5".
Mapping design into LUTs...
Running directed packing...
ERROR:Pack:946 - The I/O component "q" has an illegal IOSTANDARD value. 
   Components of type IOB do not support IOSTANDARD LVPECL_25.  Please correct
   the IOSTANDARD property value.


What am I doing wrong?  I'm still using ISE 9.1.03i.

Thanks,
Thomas
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Re: How to create a LVPECL_25 output pair (Spartan3, ISE 9.1) - John_H - 2010-07-21 18:55:00

On Jul 21, 3:23=A0pm, Thomas Heller
<thel...@python.net> wrote:
> I'm trying to create a LVPECL_25 differential output on a Spartan 3
> (XC3S200 device in PQ208 package). =A0I did this by selecting 'LVPECL_25'
> in the I/O Standard column in PACE (assign package pins).
>
> However, in 'Implement Design' I get the following error:
>
> Process "Translate" completed successfully
> Using target part "3s200pq208-5".
> Mapping design into LUTs...
> Running directed packing...
> ERROR:Pack:946 - The I/O component "q" has an illegal IOSTANDARD value.
> =A0 =A0Components of type IOB do not support IOSTANDARD LVPECL_25. =A0Ple=
ase correct
> =A0 =A0the IOSTANDARD property value.
>
> What am I doing wrong? =A0I'm still using ISE 9.1.03i.
>
> Thanks,
> Thomas

Type IOB?  Do you mean Type IOBUF?  If it's the latter, the
differential version might be IOBUFDS.

I took a look at Table 10-3: Spartan-3 Generation I/O Components on
page 321 of UG331 (v1.6) Spartan-3 Generation
FPGA User Guide - http://www.xilinx.com/support/documentation/user_guides/u=
g331.pdf
- where some of the implementation details might be less murky.

Re: How to create a LVPECL_25 output pair (Spartan3, ISE 9.1) - Thomas Heller - 2010-07-22 02:48:00

John_H schrieb:
> On Jul 21, 3:23 pm, Thomas Heller <thel...@python.net> wrote:
>> I'm trying to create a LVPECL_25 differential output on a Spartan 3
>> (XC3S200 device in PQ208 package).  I did this by selecting 'LVPECL_25'
>> in the I/O Standard column in PACE (assign package pins).
>>
>> However, in 'Implement Design' I get the following error:
>>
>> Process "Translate" completed successfully
>> Using target part "3s200pq208-5".
>> Mapping design into LUTs...
>> Running directed packing...
>> ERROR:Pack:946 - The I/O component "q" has an illegal IOSTANDARD
value.
>>    Components of type IOB do not support IOSTANDARD LVPECL_25.  Please correct
>>    the IOSTANDARD property value.
>>
>> What am I doing wrong?  I'm still using ISE 9.1.03i.
>>
>> Thanks,
>> Thomas
> 
> Type IOB?  Do you mean Type IOBUF?  If it's the latter, the
> differential version might be IOBUFDS.
> 
> I took a look at Table 10-3: Spartan-3 Generation I/O Components on
> page 321 of UG331 (v1.6) Spartan-3 Generation
> FPGA User Guide - http://www.xilinx.com/support/documentation/user_guides/ug331.pdf
> - where some of the implementation details might be less murky.

Well, the problem was that I have to instantiate an OBUFDS explicitely;
then I could set the IOSTANDARD attribute:

   OBUFDS_inst : OBUFDS
   generic map (
      IOSTANDARD => "LVPECL_25")
   port map (
      O => o,     -- Diff_p output (connect directly to top-level port)
      OB => o_not,   -- Diff_n output (connect directly to top-level port)
      I => count(3)      -- Buffer input 
   );
 
Thanks,
Thomas