The MSEL port belongs to the selection port of the FPGA configuration bai program loading mode.
These pins should be connected to zero or power, indicating high or low level. 00 means AS mode, 10 means PS mode, 01 is FAST AS mode. If you use JTAG mode, connect them to 00, JTAG mode has nothing to do with MSEL, that is, JTAG mode, MSEL will be ignored, but because they can not float , So it is recommended to connect it to the ground.
FPGA Spartan-3A DSP Family 3.4M Gates 53712 Cells 667MHz 90nm Technology 1.2V 676-Pin FBGA
FPGA Spartan-3A DSP Family 3.4M Gates 53712 Cells 770MHz 90nm Technology 1.2V 676-Pin FBGA
CPLD CoolRunner -II Family 12K Gates 512 Macro Cells 179MHz 0.18um Technology 1.8V 256-Pin FTBGA
This lends power savings to High-end Communication equipment and speed to battery operated devices.