The 16-to-32-Bit Migration Gets Smoother
By Jon Titus, Senior Technical Editor
At one time, the gulf between 16- and 32-bit processors seemed wide and deep, so engineers had a difficult time making the transition from one realm to the other. Many processor manufacturers have helped eliminate that gulf and many development boards and tools simplify the migration between those realms.
Typical 8- and 16-bit evaluation boards tend to offer more "raw" I/O direct from microcontroller (MCU) pins than do 32-bit MCU boards, which often provide complete interface circuits that connect directly to Ethernet, CAN, USB and other devices. That approach also confirms for developers that a 32-bit MCU's I/O ports work as expected and it eliminated the hassle of wiring prototype Ethernet MAC/PHY interfaces.
"When an MCU includes multimedia I/O and can process video signals, designers expect an evaluation platform will demonstrate how to use those capabilities in a real system," said Jean Anne Booth, chief marketing officer at Luminary Micro. "If you design a web-enabled industrial control, why not get a head start and work with a board that comes with a web server and source code you can adapt to your requirements?" The Luminary Micro LM3S6965 MCU, for example, comes with an Ethernet MAC and PHY and includes a ready-to-use embedded web server.
The 32-bit reference-designs boards fill a niche when developers have a demanding application. "After developers understand the motor-control capabilities of our MCUs they still might find it a challenge to figure out what it takes to efficiently drive a motor," explained Booth. "So we provide complete motor-control platforms--that include a motor--to show them how they can use the MCU for motion control. That gives them code and a working circuit to jump start their project."
"When you look at 32-bit MCUs, you see a definite trend towards more integration," said Keith Ogboenyiya, product marketing manager for the TMS320C2000 family of processors at Texas Instruments. "But engineers expect more integration in new 16-bit MCUs, too. The engineer's end product usually dictates how much integration and how many bits make sense." As an example of this demand, TI recently announced the MSP430F5xx family of low-power 16-bit MCUs that will put RF communications, USB ports and an LCD controller on these devices.
To help developers with 32-bit MCU applications, TI now offers five modular 32-bit TMS320F28x Digital Signal Controller development kits that include a controller subsystem on a 100-pin DIMM-size card. Engineers can buy several digital-power kits that let them get a project off to a quick start as they become more familiar with one of the 'F28x processors. "The majority of engineers can start a new project with a basic development kit not geared to a specific application," said Ogboenyiya. "But a reference design puts them several steps ahead in the design cycle. And the availability of 16- and 32-bit processors lets designers make cost and capability tradeoffs. When you look at 16- and 32-bit MCUs, you'll see a gradual progression in capabilities and not a gap between those two camps."
"If you look at our tools from a 16 bit perspective, you’ll see a lot of general-purpose designs that help engineers evaluate and start to work with MCUs," noted Kevin Belnap, product marketing manager for the Texas Instruments MSP430 16-bit MCU family. "But we do have system-on-a-chip types of MCUs for specific markets such as gas, water and electricity meters and medical products. So we aim some development hardware and software at developers of these types of products. In some cases, the development hardware looks a lot like a real product. For the most part, though, we offer general-purpose hardware and software tools for 16-bit MCUs."
No matter whether you simply want to become familiar with a processor family or have a specific application in mind, most likely you won't find a development system that meets your every need. "It’s impossible to build a board that matches every customer's expectations, so we recommend developers start with the Explorer 16 and then add PICtail Plus daughter cards." said Terry West, marketing manager for the High Performance Microcontroller Division at Microchip Technology. "We can't predict what I/O devices a 16- or a 32-bit developer will need, so we took an incremental approach. You buy just the add-in PICtail Plus boards needed for a project and then have them available for the next project."
"And we have development hardware for the new 32-bit PIC32 MCUs," noted West. "We have a portfolio that lets developers easily migrate between our 16- and 32-bit products, which include pin-compatible 32- and 16-bit MCUs. Engineers also use the same code, tools, libraries and PICtail Plus boards as they move from one processor to another. They simply recompile our unified-code libraries for another processor and the code works without forcing the engineers to fiddle with parameters and modify C code to get things to work. The peripheral libraries 'hide' all the hardware differences so you can pull out a 16-bit MCU and insert a 32-bit MCU, or vice versa, depending on your design requirements. And best of all, you can download the free software-development tools and, if you wish, you can start to simulate processor operations without any hardware."