an interview with geoff lees, vice president and general...

An Interview with Geoff Lees, Vice President and General Manager, Microcontrollers, NXP

Dual Processing with the ARM Cortex-M4Digital Signal Controller and Cortex-M0 MCUby Glenn ImObersteg, Embedded Developer

INTERVIEW Cortex Resource Guide Article

www.digikey.com/cortex • Fall 2010/Spring 20118 Cortex Resource Guide

NXPhas released araft of new ARM Cortex-basedproducts since ESC West inApril of this year. Recently,Glenn ImObersteg, Presidentof Embedded Developer,caught up with Geoff Lees,Vice President and GeneralManager, Microcontrollers,NXP, in Sunnyvale, Californiato discuss their 2011 roadmapand the Cortex-M4.

Glenn: There’s been a lot of activity at NXP surrounding newARM Products since you announced the Cortex-M4 at ESC.

Geoff: Our Cortex product range has gained momentum in thelast six months, and we’re coming up to an extensive series ofproduct launches for the fall embedded events. We've got a number of new Cortex-M0 and -M3 products in the low-powerarea coming out, offering improvements in both dynamic as wellas stand-by power. Customers today are more and more lookingto reduce the dynamic power component of high performancesystems in order to achieve stringent energy efficiency targets.We also announced becoming a lead licensing partner for Cortex-M4 with ARM at Embedded World, leading to EmbeddedSystems Conference in Silicon Valley where we showed firstfunctional silicon of the Cortex-M4, and we’ve been working on a lot of innovative new ideas in that series of products.

Glenn: Let’s discuss your new 90nm (nanometer) product line,first. This is based on the Cortex-M3, correct?

Geoff: That’s right -- The new LPC1800 Cortex-M3 series is designed using our new 90nm Flash process. This is an extension of our 90nm low-power process that our LPC3000

Geoff Lees, VP and GeneralManager, Microcontrollers, NXP

ARM926 family has been using since 2006, but we've spent more in the area of active leakage reduction. We've also improved ourflash interface technology on that process and are seeing majorperformance increases up to 150MHz and higher.

Glenn: So the LPC1800 is the first product in your new 90nmFlash process.

Geoff: Yes, and it’s the industry's highest performance Cortex-M3. We've implemented our new 256-bit wide flash memory interface with a dual bank safe re-programming architecture for the first time, continuing the performance advantage of NXP’s high-performance zero-wait flash. So, you’re now able to execute from one flash bank while reprogramming the other. In the first product range, we'llhave up to one megabyte of Flash memory consisting of twoflash banks of up to 512 kbytes each. In future products we'replanning to be able to offer two megabytes and later fourmegabytes of memory.

Glenn: I’ve heard the new LPC1102 is the “World’s smallest 32-bit microcontroller.” What’s happening there?

Geoff: The LPC1100 family is already allowing us to offer someincredible innovations: the LPC1102, for example, is the first 32-bit MCU in a 2 x 2 mm wafer level chip scale package. It combines an amazing 5 channels of A to D, two serial channelsand multiple timers in a tiny package. But even more incredible is the fact that it offers 32 kbytes of flash and 8 kbytes of SRAMin such a small package.

Glenn: Traditionally, the only tiny microcontrollers available havebeen 8-bit parts with 1K of program code and up to 256-bits ofram in the same package size.

Geoff: That’s right—and the difference is dramatic: the LPC1102offers thirty-two times more code and data memory size by com-parison in conjunction with 32-bit performance.

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We now have plans for a much wider range of chip scale derivatives with the addition of more analog mixed signal functionality, covering a wide spread of digital power control andconversion applications. We’re also working on offering more innovative peripherals, as well as much more on-chip memory,but maintaining all the benefits of our M0 family: low-cost, ultra-low power, reduced code size and easy-to-use--all of thoseare proving invaluable to our customers in adopting the M0, andthe ease at which our customers can now migrate to 32-bit isquite amazing. This has been the most successful and rapidadoption of any of our microcontroller series.

Glenn: Are you planning on expanding your low-cost tools solutions to keep pace with the introduction of these new devices?

Geoff: We recently extended our LPCXpresso development tool toinclude coverage for all the LPC1700 range, so that it now thatsupports all of our Cortex-M0 and -M3 families. Within the last12 months 10,000 new users have started development with ourEclipse-based LPCXpresso tools, and we can easily see from thisthe widespread popularity of open-source development increas-ing in the future.

Our LPC1768-based mbed rapid prototyping tool is primarilytargeted at new users, fast prototypes, market demonstrations,and areas where developers are looking at spending less time oncode generation and validation, and much more exploration ofnew applications of embedded technologies. We are very muchfocused on increasing the on-line database of applications andcontent, as well as improving the usability of mBed.

Glenn: Last Spring at ESC, the press reported that NXP is goingto launch a hybrid family of DSC's (digital signal controllers),that merge both DSP functionalities as well as MCU functionali-ties. What progress have you made?

Geoff: The Cortex-M4 series is being launched as the LPC4000.Importantly, this not just another Cortex-M4, in fact it’s the firsttime we've introduced the concept of dual-core processing to themicrocontroller area. Bringing high performance digital signalcontroller applications within range of Cortex-based microcon-trollers, it includes DSP instruction expansion as well as singleprecision floating point, combined with a Cortex-M0 based pe-ripheral subsystem. All of these features are very suited to powercontrol and conversion applications such as motor control, ac-dc converters, robotics, automation and industrial applictions.

In addition, other signal-processing applications such as multi-channel Audio coding/de-coding and voice recognition/synthesiswill benefit from enhanced DSP performance, really right acrossthe application range in the MCU market.

Glenn: It’s not the first DSC in the marketplace, is it? Both TI andFreescale have introduced DSCs in the past.

Geoff: No, it’s not the first DSC, but it is the first time that the digital signal control element has been based on ARM Cortex architecture and as a result developers will be able to take full advantage of the wide range of ARM software and developmenttool ecosystem including optimized DSP libraries for the M4processor. In contrast to symmetric dual core implementations,such as dual Cortex-A9 examples hitting the news recently, this isreally an asymmetric approach to integrating a Cortex-M0 basedperipheral processor subsystem. The idea is to be able to takecare of a lot of hardware intensive I/O tasks as well as regularhousekeeping, and users can then take much better advantage ofthe Cortex-M4's true DSP performance.

Glenn: So the LPC4000 DSC dual core Cortex-M4 plus -M0combines the DSP and MCU functionality of the M4 with theM0’s peripheral handling. Is anyone else offering this approach?

Geoff: Cortex-M0 is such a small processing core, around 12kgates, but it offers a lot of advantages for enhancing a user-configurable peripheral sub-system. We’re going beyond just setting up programmable peripherals on their own to a pointwhere we have a local 32-bit processor dedicated to software andhardware based I/O tasks.The M4 can just as easily be used forconventional MCU duties, in a very similar way to our LPC1800M3 family, for example. But one of the characteristics of digitalsignal control applications compared to regular microcontrolleroperation is intensive math and control computation as well asstreaming signal processing for waveform analysis, synthesis,coding and compression.

In those applications you want to be able to dedicate processorperformance to the application for a higher percentage of avail-able bandwidth than in typical MCU applications. At this point noother ARM partners who have announced M4 licenses havestated that they’re offering dual core systems, so we haven't seenany other products that include peripheral sub-system proces-sors. We believe that this is a powerful new approach for real-time control processing, which allows many customers toapproach the flexibility of a custom ASIC solution without majorcost or engineering design effort.

Glenn: Are there any other innovations in the new LPC4000’speripheral sub-system?

Geoff: To take advantage of the addition of the M0 processor,we've added a new range of configurable peripherals. Peripheralsthat go far beyond the regular range of functionality today.For example, state configurable timers that have an awarenessof the sequence and state of operations and that can benefitfrom more extensive processor interaction. So a 32-bit processorcan be combined to form a closed-loop current-control system in



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hardware, and software control loops for PID-based speed andfield control algorithms. Advanced motor control is an area thatwe specifically designed the sub-system to address efficiently.

We've also developed a special I/O cell for the sub-system, sothat the M0 (or M4) has access to and control of dedicated I/O.Functionality, such as sequential serial and parallel operations,can be combined with the M0 core to develop virtual peripheralsfar more effectively. This can be used to generate a wide range ofserial communications with special or unique protocols withoutrequiring ASIC hardware. One example that is now possible fromthe overall architecture is an audio codec software and hardwareapplication with transmission via a dedicated 7.1 channel I2Sport. The whole peripheral processing sub-system has really beenoptimized around the capabilities of the M0 sub-processor.

Glenn: Does the dual processor architecture cause problems forsystem development? What tools does an engineer need todevelop to take advantage of the LPC4000 capabilities?

Geoff: As I said earlier, the advantage of a dual core M4 and M0processor architecture is that they can be programmed at thesame time using the same integrated development environment.This uses the same project overview, the same compiler chainand the same debugging tools.

You can look at both of the cores separately, as the initial architectures are intended for a relatively low degree of softwareinteraction, or as the architecture develop further, and tool vendors respond, there will increasingly be options for simultane-ous interactive debugging.There is also the opportunity for a lotof software re-use, from a wide range of MCU functionality andapplication code that has come from our own discrete Cortex-M0LPC1100 family and can now be utilized again in the high-perfor-mance dual-core series. If you take our current LPCXpresso development tool available for under $30, you can immediatelyconnect it into current and future LPC1800 and LPC4000 products via the standard SWD connector. This is the big benefitderived from having a single scalable ARM architecture and arange of compatible Cortex cores.

Glenn: What other support material have you created to getcustomers up to speed with the LPC4000?

Geoff: We have prepared a number of white papers during recentmonths, such as working with the Quad SPI dataflash interface,the state configurable timers and the serial parallel GPIO,and those will be available at the product launch. From the verysuccessful LPC1100 Cortex-M0 family, we've already developeda number of dedicated applications in areas such as keyboardscan, serial communication handling for example and those applications and the code can be taken directly and run on the M0 sub-processor in the LPC4000.

Glenn: Where would users get the most benefit from theLPC4000 DSC solution, and when will they be able to start?

Geoff: The LPC4000 will make it a lot easier to integrate DSPfunctions and DSP assisted control to increase the performance,efficiency and range of regular microcontroller-based power control applications. Typically today an engineer would have toadd a DSP-based solution in addition to a general purpose MCU.The reason why DSP alone does not cover this type of applicationis that generally DSP's don't come integrated with highbandwidth communication peripherals such as Ethernet 10/100,high-speed USB + PHY, Controller Area Network interface. Another area where Cortex processor solutions are muchstronger than DSP devices is in interfacing to a wide range of advanced color graphics touch-screen LCD controllers.

This is all going to be in the sub-$10 price range depending onthe memory configuration. For example, the first LPC4000 products will have up to 264 kbytes of SRAM, extending the current Cortex microcontroller range significantly. NXP will bepresenting and demonstrating the LPC4000 series at Electronica2010 and at ARM TechCon 2010, and product and tools will beavailable from Digi-Key shortly afterwards. m


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