When implementing a design with large number of differential I/Os (LVDS_25, LVDS_33, MINI_LVDS_25, MINI_LVDS_33, RSDS_25, RSDS_33, PPDS_25, PPDS_33, TMDS_33), you might receive the following error if you have exceeded the number of DIFFMTB sites:
DIFFMTB / DIFFSTB sites are the Differential Standard Master / Slave Top Bottom sites. These are the only sites that can support the above standards for both inputs and outputs, so you are limited to using the Top and Bottom banks of the device for true differential outputs.
The left and right banks of the device can support differential I/O standards; however, these are limited to the following:
If you are using differential I/O standards (for example, LVDS_25) and still do not have enough pins in order to MAP your design, then there are some options available to you:
Looking at the signals at the die of the receiver, it is clear that the BLVDS_25 is compatible:
However, in order to use a BLVDS_25 output to drive a LVDS_25 input, additional termination resistors are required as shown in Figure 7 of the data sheet:
As the additional termination resistors will take up PCB space, this option might be possible only if there is a small number of LVDS_25 outputs that cannot be mapped.