Why do we show class I or class II for HSTL and SSTL input I/O standards in Quartus II software when HSTL and SSTL input standards are classless by specification? - Why do we show class I or class II for HSTL and SSTL input I/O standards in Quartus II software when HSTL and SSTL input standards are classless by specification? Description Industry standards do not define class I or class II for input HSTL and SSTL standards. The class designations only apply to HSTL and SSTL output buffers. Quartus II software allows you to choose class I or class II for HSTL and SSTL standards even through there is no difference at all. In Quartus II software it would cause confusion to have three selections: SSTL18, SST18 class I, and SSTL18 class II since it would imply you can have the SSTL18 setting for output pins. HSTL and SSTL output pins require a class setting. Custom Fields values: ['novalue'] Troubleshooting novalue False ['novalue'] ['novalue'] novalue novalue ['Programmable Logic Devices'] ['novalue'] ['novalue'] ['novalue']