STMicroelectronics (ST) has developed an ISO26262-compliant variant of its high level synthesis (HLS) flow for the design and verification of automotive image signal processors (ISPs). It says the flow allows it to generate ISP ‘templates’ within eight weeks, against 24 weeks for hand-written RTL.
ST’s standard ISP HLS platform
ST conceives an ISP as a “cascade of filters” with similar content. It has therefore developed a library of ISP templates that can be used across multiple designs and markets. These enable greater efficiency through re-use as well as freeing up staff to work on differentiated algorithms and IP blocks (Figure 1).
By then exploiting the shortened design cycles available through HLS, ST has been able to create more than 50 designs using the flow in the last two years. They have ranged in size from 10,000 to 2M gates. Since 2015 ST has used the Catapult HLS platform from Mentor, a Siemens business.
In addition, ST has also developed a modular approach to verification.
A family of UVM testbenches “specify sequences the provide pseudo-random verification and collect code and functional coverage metrics”. These are used unmodified to verify C++ code and the RTL generated from it (Figure 2).
ST’s HLS variant for ISO 26262
The ISO 26262 standard for the functional safety of automotive components sets a higher bar than for traditional multimedia ISPs. ST has therefore reviewed the standard flow to ensure that HLS provides the robustness required by the standard (Figure 3).
As part of that process, ST qualifies the simulator that runs tests on its automotive designs. As the HLS platform provider, the vendor provides ISO 26262 qualification and documentation for Catapult under its Mentor Safe program.
“The next major requirement [of ISO 26262] is to ensure that the design can handle and recover from single or transient faults,” the ST paper says. “The team confirms robustness by surrounding the ISP with external safety mechanisms such as LBIST and lockstep.”
For fuller detail on ST’s flow decisions and more on its improved delivery times using HLS, STMicroelectronics Quickly Brings Automotive Image Signal Processing to Market with High-Level Synthesis by ST Imaging Product Digital Design Manager Marc Schmitz is available for download now. Alternatively, the flow and use of HLS is described by Schmitz in this half-hour webinar.