STELLARIS®: INTRODUCING A NEW MCU FAMILY TO THE CODICO LINEUP!
ARM7 architecture has been in existence for over 10 years now, with billions of ARM7-based CPUs / MCUs in use around the globe today. Despite this impressive success record, MCU core development has not stood still, and there are several decisive reasons why a generational changing of the guard will soon be upon us - particularly when it comes to MCUs for real-time applications. Thus, it's time to meet the ARM® Cortex™-M3, a product specifically engineered to succeed ARM7-based technology.
ARM® Cortex™-M3
The ARM® Cortex™-M3 is a powerful, low-cost 32-bit processor core that minimizes memory requirements, reduces the pin count and lowers power consumption in systems where it is used, at the same time achieving exceptional processing performance and extremely low interrupt latency. With 33,000 gates, the ARM® Cortex™-M3 is the smallest processor core developed by ARM® to date. The design permits a reduction in chip surface area, thus enabling small IC packages and the use of reduced-cost 0.35µ or 0.25µ manufacturing processes. Despite its small size, the ARM® Cortex™-M3 offers an exceptional performance of 1.2 Dhrystone MIPS per MHz - better than that of many larger 32-bit processors.
Whereas ARM7 architecture permits operating the processor in either ARM® or Thumb mode only, the ARM® Cortex™-M3 operates with the Thumb-2 instruction set. The Thumb instruction set is an innovative ARM technology for reducing the required code size, and thus also the system memory requirement, which in turn helps reduce system costs. Thumb technology "links" 16-bit instructions with the ARM 32-bit RISC architecture and, by permitting the use of 16-bit instructions, significantly reduces the size of the user code. For its part, the Thumb-2 instruction set is binary compatible with existing Thumb implementations, and it furthermore supports hardware-implemented divide and single-cycle multiply instructions. Though such performance characteristics are typical of DSPs, they are not usually found in microcontrollers. Thumb-2 also supports 32-bit ARM instructions, thus making it possible to compile a compact instruction set that is efficiently supported by high level languages - one key advantage to using 32-bit architectures.
Thumb-2 enables code densities normally achieved only by 8-bit microcontrollers, but with full 32-bit performance. Figure 1 clearly shows this using the EEMBC benchmark score.
Many microcontroller applications need to execute interrupt service routines within a set timeframe. In legacy ARM7 architectures, the required time can only be forecast within a fairly broad range since the interrupt controller is not a part of the processor core, and a request must thus be sent to an external interrupt controller. The Cortex™-M3, however, integrates the interrupt controller in the core and enables up to 256 interrupts to be defined and prioritized. As a result, the time required for branching into an interrupt service routine can be precisely forecast - always 12 clock cycles. In addition, the processor implements "tail chaining" technology that permits several pending interrupts to be executed one after the other without having to exit the interrupt service routine. Tail chaining ensures that the interrupt is executed within 6 clock cycles.
Stellaris®: LUMINARY MICRO's MCU Family
LUMINARY MICRO was founded four years ago with financial participation by ARM®, and it was the first supplier to offer silicon products that implement the Cortex™-M3 core. ARM®'s participation in LUMINARY MICRO is unique and represents a long-term commitment. The fact that one of the original architects of the Cortex™-M3 core now heads MCU system design at LUMINARY MICRO is also a huge advantage in terms of product development. We are thus convinced that the future success of LUMINARY MICRO is guaranteed.
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Figure 2 shows a block diagram of the Stellaris product family
LUMINARY MICRO's Stellaris family today consists of 104 products that differ in package type, pin count, flash and RAM memory, and the type and number of implemented peripheral functions. In addition to 3 CAN interfaces, a single MCU may include I2C interfaces, an Ethernet MAC and PHY, and diverse analog interfaces and motion control functions. A useful Web tool for quickly finding the fitting Stellaris MCU for a specific application can be found at: www.luminarymicro.com/products/
product_selector_guide.html
To support ease of integration of the required functionality within the customer's overall system, LUMINARY MICRO makes available a no-cost, license-free driver library for all peripheral functions.
Another key feature of Stellaris family products is single-cycle flash access up to a (current) maximum clock frequency of 50MHz. As a result, no wait states must be inserted to access either instruction or data memory.
Cost-effective evaluation kits are available for all product series.
Figure 3 shows the Ethernet and CAN evaluation kit consisting of two boards (CAN host and slave) and the necessary cables and software.
For development tools, the Stellaris product family is supported by all leading manufacturers. Evaluation kits ship with a choice of Keil, IAR or GNU code sourcery tools. The scheduled addition of variants with USB interfaces will keep the Stellaris family growing in the coming months.
Summary
By implementing the ARM® Cortex™-M3 in its Stellaris product family, LUMINARY MICRO has achieved an engineering development that is at once cost-effective, performance-enhancing and - thanks to its ARM architecture - full of future promise. With a broad range of development tools already available, the company's ARM® Cortex™-M3-based microcontrollers have the potential to push 8-bit and 16-bit devices from their traditional application fields. With a wide variety of interfaces and analog functions to choose from, the Stellaris family is especially well suited for automated industrial control and motion control applications, e.g., as found in today's energy-efficient electrical drives (brushless DC motor controllers, etc.).
CODICO looks forward to a successful cooperation with LUMINARY MICRO, and we a re proud to have added another innovative and reliable partner to our ARM-based microcontroller linecard.
I look forward to answering your questions and inquiries!
Werner Reis, Tel: +49 8141 357 264
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