Cyclone® V Device Handbook: Volume 1: Device Interfaces and Integration

ID 683375
Date 10/18/2023
Document Table of Contents

7.13.3. Security Key Types

Cyclone® V devices offer two types of keys—volatile and non-volatile. The following table lists the differences between the volatile key and non-volatile keys.

Table 102.  Security Key Types
Key Types Key Programmability Power Supply for Key Storage Programming Method
  • Reprogrammable
  • Erasable
Required external battery, VCCBAT 24 On-board
Non-volatile One-time programming Does not require an external battery On-board and in-socket programming 25

Both non-volatile and volatile key programming offers protection from reverse engineering and copying. If you set the tamper-protection bit, the design is also protected from tampering.

You can perform key programming through the JTAG pins interface. Ensure that the nSTATUS pin is released high before any key-programming attempts.

Note: To clear the volatile key, issue the KEY_CLR_VREG JTAG instruction. To verify the volatile key has been cleared, issue the KEY_VERIFY JTAG instruction.
24 VCCBAT is a dedicated power supply for volatile key storage. VCCBAT continuously supplies power to the volatile register regardless of the on-chip supply condition.
25 Third-party vendors offer in-socket programming.