Hi,
- What are the process that you can do and you cannot do now?
What I can do : Flash FPGA configuration file in EPCQ
What I cannot do : Load a design into FPGA and program encryption key
- Can you program JTAG, AS?
I can program EPCQ with AS. I cannot program FPGA with JTAG because JTAG is in secure mode.
- Per my understanding, you cannot load the design into FPGA through due to you do not have the key? You can try to replace the flash and program again
Indeed I cannot load the design into FPGA but it has nothing to do with the flash.
My problem seems to be confusing so I will try to explain it again through a user case :
- I try to load an unencrypted design into FPGA but it doesn't work. Why ?
- Because I activated tamper bit protection (which is irreversible). What does tamper bit protection mean ?
- It means that only encrypted FPGA configuration files are accepted. No worry ! I just have to encrypt my design. I do it but FPGA configuration step fails. Why ?
- Because FPGA needs the encryption key to be able to decrypt the design. Let's try to program this key on FPGA. It fails. Why ?
- Because JTAG is in secure mode. What does JTAG secure mode means ?
- It means that I cannot program a device and I can only issue mandatory JTAG commands. Why is JTAG in secure mode ?
- Because I activated it when I enabled tamper bit protection. Is there a way to disable JTAG secure mode ?
- Yes ! There is one way : by issuing UNLOCK command. For 28nm devices (my device), you can only issue UNLOCK command through JTAG internal interface. How do I access JTAG internal interface ?
- By adding a specific module in my FPGA design. Let's do this and configure FPGA with this new design. Configuration fails. Why ?
- Back to step 1 : I cannot load a design into FPGA.
The question is : Considering this tamper bit activation, is there a way to configure FPGA ? Or a way to program a key ? Anything that could allow me to configure FPGA
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