[Blog] Innovations in SRAM-based FPGAs: Fast, Secure Boot Times Explained

In the world of programmable logic devices, SRAM-based FPGAs are often misunderstood. These FPGAs offer incredible flexibility and reconfigurability, making them ideal for a wide range of applications from consumer electronics to aerospace. Additionally, SRAM-based FPGAs can achieve high performance and low latency, making them suitable for demanding tasks such as real-time data processing and high-speed communication.

It's a common misconception that SRAM-based FPGAs are burdened by lengthy boot times. The argument often goes that because their configuration data is stored off-chip, especially when encrypted and requiring authentication, the process of loading this information onto the FPGA becomes a bottleneck. However, this perception doesn't hold true for many modern SRAM-based FPGAs, and the Lattice Avant™ FPGA platform stands as a prime example of how innovation is shattering these boot time limitations – offering 10X faster boot times than similar class FPGAs.

Lattice Avant FPGAs are mid-range FPGAs that utilize SRAM technology for their programmable fabric, meaning the configuration is volatile and must be loaded upon power-up. This configuration data, or bitstream, is typically stored in an external non-volatile memory like an SPI Flash or MRAM. Furthermore, for enhanced security, Avant devices support robust bitstream encryption using AES-256-GCM and authentication through ECDSA or RSA. The use of configuration file encryption is dependent on the additional step to manage secret keys. This management includes the generation of the keys, the program’s storage of the keys, secure injection of the keys into the FPGA devices, and security architectures to protect, revoke, and update keys.

Lattice Avant FPGAs employ a multi-layered approach to key management, leveraging a unique Hardware Root of Trust called a Physically Unclonable Function (PUF), secure factory provisioning, flexible user key generation and storage options (eFuse and BBRAM), and a secure boot process with robust bitstream encryption and authentication, all managed within the dedicated embedded security block and configured through the Lattice Radiant software. For more details, download the user guide here.

However, the notion that these factors inherently lead to long boot times overlooks the sophisticated techniques employed by Avant FPGAs to ensure fast and efficient system bring-up.

Let's debunk the myths by exploring some of these key innovations:

• Early I/O Release: One of the most significant contributors to the fast boot capability of Avant FPGAs is the early I/O release feature. This technique allows specific I/O banks on the left and right sides of the device to become active and assume user-defined drive states at the very beginning of the bitstream processing. This means that critical system interfaces can be initialized and functional much earlier in the configuration cycle, leading to instant-on responsiveness for the overall system. Instead of waiting for the entire bitstream to load, the system can begin interacting with the FPGA's I/Os in less than 5 milliseconds (ms).
• Ultrafast Configuration Interfaces: Avant FPGAs boast high-speed configuration interfaces using Serial Peripheral Interface (SPI). This interface supports various modes (serial, dual, quad) with the high-performance Octal SPI (x8, dual transfer rate), reaching speeds up to 160 MHz. These fast interfaces enable rapid transfer of the bitstream from the external memory to the FPGA's configuration SRAM, significantly reducing the overall configuration time. The device also initiates the boot process with a fast signature verification and preamble verification phase to expedite the loading.
• Bitstream Compression: To further accelerate the configuration process, Avant FPGAs support bitstream compression. By compressing the configuration data, the size of the bitstream stored in the external memory is reduced by up to 75%, leading to faster download times over the configuration interface. The FPGA then efficiently decompresses this data during the configuration process.
• TransFR (Transparent Reconfiguration): While primarily focused on minimizing system disruption during updates, TransFR technology also highlights the efficiency of the Avant configuration process. It allows for background programming or reconfiguration of the non-volatile memory while the FPGA continues to operate. When a reconfiguration is initiated using TransFR, the I/O states are captured to maintain system stability during the SRAM update. This capability underscores the speed and controlled nature of the configuration mechanism.

Watch this video of the incredible boot up speed of the mid-range Lattice Avant™-G FPGAs. With a significantly faster boot-up time compared to similar class competitive devices, Lattice Avant FPGAs make them a go-to choice for security and safety-critical applications.

In conclusion, while SRAM-based FPGAs like the Lattice Avant do rely on off-chip configuration storage and offer advanced security features like encryption and authentication, they are not inherently slow to boot. Through innovative techniques such as early I/O release, ultrafast configuration interfaces, bitstream compression, and efficient reconfiguration mechanisms like TransFR, Lattice Avant FPGAs effectively counter the misconception of long boot times, delivering rapid system bring-up and enabling a wide range of high-performance applications. The focus is not just on security and flexibility, but also on ensuring a seamless and fast user experience right from power-on.

To learn more about how Lattice FPGAs can help enable high-performance applications, reach out to our team today.