1.Location Constraint ? 用于分配I/O端口
NET <I/O_NAME> LOC = "<EXTERNAL_PORT_IDENTIFIER>";
Example:
NET MY_IO LOC=R7;
2.IOSTANDARD Attribute 用于選擇IO標準如LVCMOS25，LVDS_25等
NET <I/O_NAME> IOSTANDARD=”<IOSTANDARD VALUE>”;
3.Output Slew Rate Attributec?
NET <I/O_NAME> SLEW = "<SLEW_VALUE>";
SLEW_VALUE can?SLOW (Default) ??FAST ?QUIETIO
4.Output Drive Strength Attribute 驅動能力（mA）
NET <I/O_NAME> DRIVE = "<DRIVE_VALUE>";?
DRIVE_VALUE can 2 4 6 8 12?(Default) 16 24
5.PULLUP/PULLDOWN/KEEPER for IBUF, OBUFT, and IOBUF?
NET <I/O_NAME> <PULLUP/PULLDOWN/KEEPER>;
?
