Support for the EPCS128 serial flash memory device is added in NiosII version 9.0. If you are using Nios II version 8.1, you will not be able to access an EPCS128 device using the version 8.1 factory installed drivers. If you have version 8.1, and need to access an EPCS128 device, download this patch to enable Nios II EPCS128 support in version 8.1.
To install the patch, extract the zip file and copy the extracted files to the following locations:
epcs_commands.c : <version 8.1 install>/ip/altera/sopc_builder_ip/altera_avalon_epcs_flash_controller/HAL/src
epcs_commands.h : <version 8.1 install>/ip/altera/sopc_builder_ip/altera_avalon_epcs_flash_controller/HAL/inc:
altera_avalon_epcs_flash_controller.c : <version 8.1 install>/ip/altera/sopc_builder_ip/altera_avalon_epcs_flash_controller/HAL/src