Within the MachXO2 device, the settings for LVDS25 and LVDS33 are identical, the only difference is the voltage level applied to VCCIO. So to implement the IO's as LVDS33 in Lattice Diamond the IO's are set to LVDS25. The user then needs only apply 3.3V to VCCIO.
The user must be careful not to mix LVDS25 and LVDS33 in the same bank because the Vin and Vcm(common mode voltage) are different for each of the IO Types LVDS25 and LVDS33. Also, user must be sure to follow the MachXO2 datasheet LVDS spec on page 3-9"Over Recommended Operating Conditions" (MachXO2 Family Data Sheet).
If user has both LVDS25 and LVDS33 I/Os in their design, to be able to place LVDS25 and LVDS33 into different IO banks, for example, LVDS33 in Bank1 and LVDS25 in Bank2, user has to set preference as follows:
IOBUF GROUP "bank2" IO_TYPE=LVDS25 BANK=2;
BANK 1 VCCIO 3.3 V;
BANK 2 VCCIO 2.5 V;