I write DFh to address 0 on "EPM240T100C5N" by the programmer, security is imposed on the CFM area and only 00 can be read. Is it possible to explain why security is applied even though Security bit is not set ?

Hi TTsujo6,

Did you perform erase operation first before program operation? Make sure all the power supplies are correctly powered up before any operation. Did you power cycle the EPM240 device after program the CFM before perform the verification process? Please do not perform power cycle between any processes. As explain in the MAX II device handbook under Chapter 3: JTAG and In-System Programmability, the programming sequence should be Power up ->Enter ISP ->Check ID->Erase ->Program ->Verify -> Exit ISP ->Power down.

https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/hb/max2/max2_mii5v1.pdf

How did you get/generate this DFh data? If you are using your own programmer, then you should be referring to the .pof or .svf file for the correct data that need to be write into the CFM memory block. You should convert the .pof file into a .svf file. The .svf file contain all the correct programming sequence and data that user can use to program the CFM + UFM. You can refer to the how to video on the steps to generate .svf file:

https://www.youtube.com/watch?v=L4R2NKekttw

Regards,

Nooraini