FPGA Platform Allows Faster Implementations

New Help for the FPGA-Challenged: VeriLog Is a New Language You Should Know

Jeremy PollardBy Jeremy Pollard

Embedded intelligence exists in many places, as I discovered with a very cool text editor called Notepad++ that I use for development work. It will format the text you are viewing in various languages, including two called VHDL and VeriLog. I had used VHDL, but I had no idea what VeriLog was.

Verilog is the language of field programmable gate arrays (FPGAs), which are used in embedded controls and fixed-board systems where the user has no interactions.  But when SoftPLC sent me the skinny on its new Smart line of PLC/PAC hardware that included FPGA technology, I wondered why that mattered.

So I asked Dick Hollenbeck, the technical guru of SoftPLC, why it now was important to mention FPGA technology in something having to do with industrial control.

FPGAs, he explained, are configurable hardware blocks that accept software "cores," which then give the hardware the personality it needs for the function that you design.

But, he emphasizes, there is no software component involved. "The FPGA becomes a microprocessor once a core is downloaded, but it's very fast because the FPGA can do sequences in parallel on the same clock cycle, just like the old relay ladder logic did," says Hollenbeck.

Dick is very passionate about this technology. He always has been one to do things that were technically challenging, but that gave his customers a better way to do things.

But to be clear, the value is in the machine builder's shop, not the user's. The FPGA platform allows the machine builder to design and build very fast implementations of functionality that is not software-based, per se. And that's where VeriLog comes in.

Hollenbeck describes the FPGA as a malleable printed-circuit board. The transistors are there, and you connect the dots using VeriLog, which can be described as a core. Once downloaded, the FPGA becomes that function, which is stored in onboard flash memory.

You can create protocol as well. Imagine having an FPGA that has your own protocol for diagnostics or an OPC routine onboard.

"The circuits are created when you download the core and glue together the TTL nodes," says Hollenbeck, creating look-up tables, or LUTs.

He described a use for the FPGA technology for SoftPLC's Smart controllers. The design incorporates a pin header that can accept a daughter card of any design as long as it conforms to the pinout. Hollenbeck says having a daughter card with multiple FPGAs onboard means you can create a system with unlimited serial ports, if needed, because the universal asynchronous receiver transmitter (UART) portion of the serial port can be created in the FPGA as a serial core, thus allowing the host system—SoftPLC's Smart controllers—to interface with multiple serial ports in parallel. Multiple TCP stacks or DeviceNet stacks also could be present on the same daughtercard, if so desired.

As I say, this is an OEM world technology. Designing a one-off system could prove to be uneconomical.

VeriLog is a development language that would take some time to become familiar with. It takes some getting used to. The syntax is very "assembler-like," a language with which most of you (I'm older than I look) might not have had the privilege to use. Having said that, there are select statements and procedural-type statements and function declarations that allow the developer to create a comprehensive core that will run very fast.

I can see motion control functionality and other applications that require fast processing being a lucky recipient of this technology and applications where the value of the process is in the intellectual property, which can be protected in an FPGA. As Hollenbeck states, "There is no jitter in an FPGA motion system." Any application that has an IP component could be placed in the FPGA.

The FPGA and Programmable Logic Journal online (www.fpgajournal.com) deals with various embedded control issues. It includes descriptions of the level of protection you need to build into your design to be sure that your IP is locked solid.

Big automation suppliers might use FPGA technology in their designs, but the user would never know. The problems that this technology solved for the OEM/vendor are invisible to the user.

But the machine builder can rest easy on its control designs, knowing that they will work well and be repeatable, fast and protected.