Boasting better than 60,000 customers, Microchip claims to be the king of the 8-bit microcontroller hill. But it's the 32-bit mountain that Microchip sees in its future. To that end, the company has developed its first 32-bit microcontroller unit, dubbed the PIC32. The device incorporates a MIPS32 M4K processor core, surrounded by all the peripherals you would expect in a PIC-based microcontroller.
“We have customers that continually ask for higher performance and more memory,” said Patrick Johnson, director of Microchip's high-performance MCU division. “It was the natural evolution for us to move up to support our customers who wanted to be on that path. We're giving our 60,000 customers a family that's compatible among 8, 16 and 32 bits, and a way to migrate up or down.”
My first question when I heard about the MIPS-based products was, “why not develop your own core?” And I really liked the answer. An obvious reason is that you can get to market much more quickly by employing an existing core. But more important, it gives Microchip and its customers access to the existing ecosystem that surrounds the M4K.
“We could have gone in lots of different directions with this offering,” said Johnson. “We could have chosen a 500-MHz core, or a superlow-power version. But that didn't make sense for the majority of our customers.” The MIPS core was chosen after Microchip evaluated a host of other alternatives, such as those offered by ARM, ARC and Tensilica.
It took about two years from the time the decision was made until samples were ready. While that seems like a long time, Microchip wanted to be sure that every last detail had been addressed, including having development kits ready for shipment. The company said it had working silicon for more than six months, and it has already gone through one revision of the product.
Microchip also wanted to ensure that all the external modules developed for the 16-bit MCU would work transparently with the 32-bitter. And the crop of analog components that work with the 8-bit family can all be used for 32 bits. Those analog parts generally operate at 3 volts, and the MCU can operate between 2.5 and 3.6 V. A standard voltage regulator can be employed.
An interesting feature of the M4K core is that it has an extensible instruction set, so Microchip can add instructions to optimize a microcontroller for specific applications.
The family is being manufactured by Taiwan Semiconductor Manufacturing Co. It's in a 0.18-micron process, beyond the current capabilities of the Microchip fabs (which go down to 0.25 micron). The plan is to continue with the TSMC fab for the foreseeable future.
While any silicon vendor can license the MIPS core, Microchip believes it offers some key advantages, starting with the migration path from 8 to 16 to 32 bits. And the MCU offers features that Microchip's existing customers have embraced, such as reset and code detection, brownout reset detection, the ability to push the voltage range beyond ±10 percent, two-wire debug modes, low pin counts, and development with tools already in their arsenals.
“We've found that our customers are almost immediately productive because the PIC32 environment looks like what they're already familiar with,” said Johnson.
In addition to being a MIPS licensee, Microchip had some input into the core itself. For example, the core's trace capability borrows some of Microchip's technology, as it consumes fewer pins and gates than a traditional MIPS product. Another example is the complex breakpoints, as the architecture now contains a sequential breakpoint capability. And the number of shadow register sets has been extended to increase performance.
The new Microchip product will benefit from the support of both internal and external ecosystems. This means that at launch time–Microchip will officially unveil the MCU Nov. 12–all the partners will announce their support for the PIC32. This includes embedded real-time operating system support from CMX Systems, Express Logic and Micrium, among others. Integrated development environments (IDEs), compilers and debuggers will be available from Ashling, Green Hills Software and Hi-Tech Software. And GUI support will be offered by EasyGUI, Micrium, Ramtex and Segger.
These third-party tools and IP are in addition to Microchip's offerings. The MPLab IDE has been upgraded (to version 8) to include everything that's needed to support a 32-bit MCU. It can be downloaded free from Microchip's Web site. The IDE works with the existing in-circuit emulator (ICE) probes. Two versions of the 32-bit C compiler are available. The “student” version is free, but it only supports up to 64 kbytes of memory. The full version sells for $1,195. An in-circuit debugger and emulator are also offered.
One of my favorite tools is the PIC32 Starter Kit ($49.95), which lets you quickly get involved in serious design. Unlike the previous-generation starter kit, which was housed in a “USB stick,” the PIC32 version has a full, expandable connector on the back, although it's still USB-powered. Using this connector, a designer can connect a series of expansion boards.
Included with the starter kit are sample projects, 35 code examples, full documentation, and TCP/IP and FAT16 stacks. The expansion boards that will be available by the end of the year include Ethernet (with an RJ45, an SD card slot and an OLED display); a QVGA display (with a touchscreen interface); and an I/O expander. The expander lets designers connect a series of daughterboards, called PICtails, that are offered by Microchip.
The PIC32 family initially comprises seven members. They all run at 72 MHz but one, which runs at 20 MHz. Microchip claims that the core runs at 1.5 Mips/MHz, which calculates to 108 Mips at the high end. With some tweaks to the compiler, that number may go even higher.
The key difference among the various parts in the family is the amount of memory that each contains. The flash runs from 32 to 512 kbytes, while 8, 16 or 32 kbytes of RAM are available (and the part can execute from RAM). Each part contains 16 10-bit ADC channels and zero to four DMA channels, five timers, two UARTs, and SPI and I2 C interfaces. Nine power-saving modes are available.
Some enhancements were made to simplify debugging because the 8- and 32-bit worlds traditionally use different debug methods. As a result, Microchip decided to incorporate both methods: its standard two-wire interface and JTAG. Furthermore, the hardware breakpoints can save debugging time.
All of the parts are housed in TQF packages, with either 64 or 100 pins. Unit prices for 10k orders run from $2.95 to $5.30. Volume production will commence in the second quarter.
Some additions being considered for the next generation of parts include USB, Ethernet, more memory and higher frequencies. Microchip wouldn't comment, but it would come as no surprise if a second M4K core appeared within the same silicon.
In addition, plans include parts that can withstand higher temperatures, for the automotive market.