You may get this error when trying to configure an EPCS device via Serial Flash Loader where the Altera® FPGA device is in a JTAG chain with devices from other vendors.
To remedy this problem, perform the following in the Quartus® II Programming window:
1. Perform Auto Detect so that Quartus II Programmer can read all the JTAG IDCODE from the devices on the JTAG chain.
2. From the Edit menu, click Add Device
3. Scroll down to the bottom of the Device Family column and highlight "User Defined" - there should be a list of devices named UNKNOWN_<JTAG_IDCODE>
4. Highlight the unknown device and click Edit
5. You may rename the Device name so it will not be shown as UNKNOWN_<JTAG_IDCODE>
6. Change the instruction register length per the device information. Typically the instruction register length information can be found in the device BSDL file
7. Click OK to save the information