The ISE 9.1i design tools report an incorrect error message restricting certain differential I/O standards from being in the same bank in Spartan-3 FPGAs.
LVDS_25 and LVDS_25_DCI in the Same Bank
When placing an LVDS_25 I/O and LVDS_25_DCI I/O in the same bank, the Place and Route tools report the following error message:
This error message is incorrect. The two I/O standards are allowed in the same bank.
This issue is fixed in ISE 9.2i SP1. To avoid this issue the user must upgrade to a version of ISE 9.2i SP1 or newer.
Differential Inputs in the Same Bank
From the documentation in a previous version of the data sheet, it appears that only one of the following can be in the same bank: LVDS, LDT, LVDS_EXT, and RSDS.
This statement is partially true. If you are using these standards as inputs only, there is no such restriction on the bank. Starting in the ISE 9.1i design tools, Place and Route errors out if more than one of these inputs are put in the same bank.
The tools also error out if one of these outputs and any number of these inputs are in the same bank. This issue is fixed in ISE 9.2i SP1.
The data sheet has now been changed to correctly state the following:
The Organization of IOBs into Banks
Only one of the following standards is allowed per bank:
LVDS outputs, LDT outputs, LVDS_EXT outputs, or RSDS outputs.
For more information on compatible I/O standards, see the Spartan-3 Data Sheet at: