Pin assignment problem!!!

[syedahmar]

Hello all!!!
i have designed a transmitter and the output of this transmitter is one pin..Now the requirement is that the transmission be done on differential lines and that means that i have to assign my output pin to LVDS standard and that has two output pins...
The problem is that i go to the constraint editor and i make my pin IO standard as LVDS_25 but in the pad report it assigns only one of the two pins and the IO standard it shows is LVCMOS.......
the device i am using is spartan 3 and the software is xilinx ISE..\
help plz....

 

[Renjith]

did u use PACE tool or
created text file for entering the pin constraints

 

[syedahmar]

well what i did was that i added a constraint file and then i double clicked on it and a constarint editor GUI opened and there i assigned my single pin and I/O standard of LVDS but it dint work.....
do we need to initialize some hardware for differential signalin b4 use as well??

 

[Renjith]

hi syed,
u can take another approach also.
open PACE editor for putting pin constraints.
in this select the pins u want to assign to particular stds.
in the window , u will c an option called"iostd".
in the select the standard u want and then save it.
hope now it shud b ok.

 

[Sandeep Karkera]

Hi syed,
did you check the other patner pin of the LVDS 25 is asigned some where else.