Spartan-6 I/O Banking Rules - Output I/O Standard Restrictions
In Spartan-6 FPGA, there are banking rules which must be followed when pinning out your design. There are some I/O Banks that do not support certain output I/O Standards. This Answer Record summarizes the I/O Standards that are not supported as OUTPUTS by each bank.
The following information is also available in Chapter 1 of the Spartan-6 Select IO User Guide (UG381), which should be used as the absolute reference for banking rules. The section below summarizes which outputs are not supported in the following banks.
Output I/O Standards which are not supported in Banks 0 and 2 (top and bottom):
LVCMOS25 24 mA Drive
LVCMOS18, LVCMOS18_JEDEC 24 mA Drive
LVCMOS15, LVCMOS15_JEDEC 16 mA and 12 mA Drive
LVCMOS12, LVCMOS12_JEDEC 12 mA and 8 mA Drive
Output I/O Standards which are not supported in Banks 1, 3, 4, and 5 (left and right):
* LVPECL25 and LVPECL33 are not supported as an output in any bank on Spartan-6 FPGAs.
In addition to these standard rules, there are Bank Compatibility rules based on VCCO voltage and other I/O Standards used which must be followed. Those are not covered in this Answer Record. The following sections should be closely read for I/O banking rules in the Spartan-6 FPGA SelectIO Resource User Guide:
The rules for I/O bank and VCCO voltages can be found in the "I/O Banking Rules" section
The rules for Single Ended I/O Standards can be found in "Table 1-4: Spartan-6 FPGA Single-Ended I/O Standard Bank Compatibility"
The rules for Differential I/O Standards can be found in the "Differential I/O Standard Bank Compatibility" section