DESIGN TOOLS: SpiraTech speeds chip bus models -

DESIGN TOOLS: SpiraTech speeds chip bus models


Santa Cruz, Calif. — The difficulty of developing bus-functional models is “the nasty, dirty, horrible secret of EDA,” according to Simon Calder, CEO of SpiraTech Ltd. The company aims to make BFMs easier to handle with its release of Cohesive Generator 3.0, a tool that can automatically generate synthesizable Verilog BFMs.

SpiraTech (Manchester, England) is also about to announce the opening of its first U.S. office. The new facility will open in San Jose, Calif., in July, staffed by several engineers. SpiraTech, a 15-person company, already has U.S. customers, Calder said, although he wasn't able to provide names.

SpiraTech's founders developed languages and tools for Fujitsu's International Computers Ltd. subsidiary in the 1990s, including the VHDL+ language. Following its launch in 2000, SpiraTech developed CY, a formal, declarative language that uses assertions to describe protocols. SpiraTech's Cohesive tool set was rolled out in 2003 as a bridge between electronic system-level and RTL design.

Today, SpiraTech positions the Cohesive Generator as the only tool that can synthesize transactors and compile bus-functional models. Transactors, according to SpiraTech, are the portions of BFMs that generate and recognize timing and patterns. BFMs represent protocols at different levels of abstraction.

BFMs, said Calder, are required in order to link transaction-level models at different levels of abstraction–including programmer's view, programmer's view with timing, cycle callable, RTL and FPGA prototype. BFMs connect testbenches to simulators, emulators, debuggers and visualization tools. If a testbench is at the transaction level or is untimed, Calder said, it will have to be rewritten at the register transfer level–a daunting task–unless a BFM is available.

“In reality, there is no kind of verification tool–simulators, analyzers, debuggers, emulators–that doesn't require a constant supply of BFMs,” Calder said. Yet writing a synthesizable BFM for a given protocol may require 100,000 or 200,000 lines of code, and represent an effort equivalent to several man-years, he said. Thus, he said, only the world's top electronics companies have the resources to write their own BFMs. Others buy BFMs from the EDA companies, but those handle only a few of the most popular protocols, Calder said.

Cohesive Generator, in contrast, promises to compile BFMs following about three man-months of effort. To use it, designers write assertions using SpiraTech's CY language. Cohesive Generator creates the transactors, creates the databases and compiles a BFM that serves multiple levels of abstraction.

Direct compilation
Until now, however, Cohesive Generator compiled BFMs written in C++, and supplied wrappers so the models could be used with SystemC and Verilog simulators. With the new Cohesive Generator 3.0 release, the tool directly compiles synthesizable Verilog BFMs.

The big win, Calder said, comes with emulation and FPGA prototyping. Without a synthesizable BFM to link a transaction-level testbench with an emulator, it's impossible to run the emulator at full hardware speeds, he said. “There's no point in doing emulation or prototyping if you don't have a synthesizable BFM,” Calder said.

CY is a proprietary language, but there hasn't been a lot of resistance to its use, Calder said. “The people we're talking to are motivated to find a solution,” he said. Calder said that CY is “very intuitive” and is similar to SystemVerilog. He also said that SpiraTech wants CY to become an industry standard, and is currently talking with large customers to gain support for that effort.

Cohesive Generator supports a variety of protocols, including AXI, AHB, APB, PCI Express, Ethernet, USB, HDMI, CAN, UART and DDR. Other standard and proprietary protocols can be supported within three months, the company said.

As for the U.S. office, Calder simply said, “It's time. The demand is there.” He said the San Jose site will provide sales and support, and will be staffed with “top-class” R&D engineers. In fact, Calder noted, he's the only sales and marketing person in the entire company–“it's me and 15 R&D engineers,” he said.

Cohesive Generator 3.0 is available for $300,000 for a site license. It's expected there will be one license per site. Cohesive Probe is a $30,000 debug tool aimed at individual developers. The Transformer BFM Linker is $1,500 per year for a run-time license. SpiraTech also sells off-the-shelf BFMs, but the company's primary focus is tool sales, Calder said.

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