Category: Specifications
Tools: Quartus® II
Device: Cyclone® IV


To use the nCEO pin as a user I/O pin, you must compile with the following settings in Quartus II.

Assignments menu ⇒ Device ⇒ Device and Pin Options... ⇒ Dual-Purpose Pins ⇒ select Use as regular I/O in nCEO

By default, it is a pin for configuration.

Note that this pin is used as a configuration pin in multi-device configuration when connecting to the nCEO pin of the previous device and the nCE pin of the following device with a 10 KΩ pullup on VCCIO. .

Please refer to the device handbook for details.
https://www.altera.com/en_US/pdfs/literature/hb/cyclone-iv/cyiv-51008.pdf
(Search with the keyword Multi-Device Configuration.)