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ESE Magazine Jan/Feb 06 40 The fourth RTOS Kevin Pope, Quadros Inc. Cores combining MCU and DSP architectures require a different kind of RTOS. THE EMBEDDED software market has historically developed two fundamentally different RTOS architectures, each designed to serve the needs of the underlying processor architectures; specifically MCU’s (CISC/RISC) and DSP's. Most commercial RTOS vendors have developed solutions adapted and optimized to one or other of these designs and their (traditionally somewhat different) applications. A third RTOS design, multiprocessor, is required to support multiple processor architectures, completing the “traditional” RTOS space. In recent years, however, the pressure to reduce both cost and power consumption in volume applications such as consumer hand-held multimedia electronics has increased dramatically. Consumers are driving their objects of desire smaller and smarter. There are many issues for the manufacturer, but the essential question has to be – how to fit more features and functions into an ever decreasing physical space. Inside the glossy exterior, there is a struggle for space on a PCB already overcrowded with connectors for USB, antenna(s), power, flash, etc. Convergent processors These market pressures have led to the emergence of a new type of single core hybrid, or convergent processor, combining both MCU and DSP architectures. Such ‘convergent’ processors can be designed as DSP's with MCU capabilities (e.g. Freescale’s DSP56800E) or MCU’s with DSP extensions (e.g. Freescale's ColdFire) or completely new cores designed from the ground up to serve both architectural needs (e.g. StarCore, or ADI's Blackfin). These single core designs enable hardware engineers to reduce chip count and reduce the overall size of the device, leading to a reduction in system cost and power consumption. But this creates a challenge for the design of the supporting RTOS architecture: should it be Table 1: Single stack advantages Multitasking Architecture for Control Plane Processing optimized for the interrupt-driven control environment of the MCU, or for the data-flow environment of DSP? In the same way that silicon has been forced to converge, a fourth RTOS type, optimized for the convergent environment is also needed. Quadros Inc have recognized this trend by developing a 4-way RTOS design, RTXC Quadros, with a version designed and optimized for each of the four architectural types; MCU, DSP, Multiprocessing, and ‘Convergent’. The approach taken to provide a convergent software solution is to use a “dual mode” RTOS design, with each part of the application running in an environment optimized either for DSP or MCU execution. Context overhead The main drawback of a multi-tasking MCU type RTOS for a DSP engineer is the necessity for each task to retain what is known as a context. This storing and restoring of data consumes vital processor instruction cycles and delays processing of the interrupt. When the interrupts are frequent and constant, as in streaming media, the context switch becomes a heavy overhead in the system. In the worst case, the control application may never get any processor time to complete its necessary processing or the interrupts may be lost because the ISRs cannot keep up with the demand from external events. With a convergent processor, these two roles must be balanced efficiently within a single resource. The obvious way to assist this situation is to reduce overheads and the biggest Multithreaded Architecture for Data Plane Processing One stack per task All threads use single stack Multiple priorities Multiple priority levels Preemption between priorities Preemption between levels Context saved and restored as needed No context saved or restored except on preemption Can wait for an event Cannot wait for an event Lower priority than threads Run to completion within a level The question is how to fit more features and functions into an ever decreasing physical space overhead in a system with many interrupts is the context switch. The dual-mode design of RTXC/dm combines a traditional task-based kernel architecture for real-time control processing with a specialized executive for DSP and dataflow operations. The control application code will execute in the familiar environment of a pre-emptive priority based scheduler, typically used for such tasks as user interface, communication paths and peripherals. Meanwhile, the signal processing application code will execute in a highly efficient single-stack environment. (See Table 1). Fast switching DSP processes, handled by lightweight code entities called threads, run at a priority higher than control tasks, ensuring they get access to the CPU and can meet their real-time requirements. Thread-to-thread switching is very fast because threads carry no context. Control operations are supported by a multitasking processing model with a rich set of static and dynamic kernel objects and inter task synchronization options. As a further advantage, all this takes place in a single development environment, so both DSP and MCU-based development tools can communicate easily between the domains using the object classes and related services of the operating system. Thus the use of a dual mode RTOS architecture ensures that the developer of such demanding applications can fully leverage the low cost, low power advantages of the new convergent processor designs emerging in the market today. www.quadros.com
• Q u a l i t y a n d r e l i a b i l i t y b y d e s i g n • L o n g t e r m s u p p l y • MAT 1100 • Intel ® Pentium ® M Processor 1.4, 1.8, 2.1G • 5V only PICMG 1.0 • -30°C option • Ideal upgrade for Pentium ® III and Pentium ® 4 designs • Far lower power than the Pentium ® 4 • Intel ® Extreme 2 Graphics • Optional High Performance Graphics using ATI 9000, dual screen, DVI/DFP, LVDS • 2 Serial, 4 USB, dual Gigabit Ethernet, Sound, CompactFlash MAT 1111 • Intel ® Pentium ® M Processor 1.4G (738), 1.8G or 2.1G • Intel ® Celeron ® M Processor 600Mhz • Low power 12 watts to 36 watts depending on CPU and loading • EBX size, Mini PCI, PC/104-Plus, CompactFlash • Heat spreader plate to support sealed system design • Fanless option • Extended temperature -30°C power on option • Intel ® Extreme 2 Graphics, LVDS, CRT • High Performance Graphics using ATI, dual screen, DVI/DFP • Two independent video input channels; mux up to 4 inputs • 5V only Contact us Europe & rest of world: Microbus plc Tel: +44 (0) 1628 537333 Fax: +44 (0) 1628 537334 email: sales@microbus.com www.embedded-pc.com Designed and manufactured in the UK PERFORMANCE IN THE EXTREME USA & Canada: Microbus Inc Tel: +1 (800) 688-4405 or (281) 568-4744 Fax: +1 (281) 568-4604 email: sales@microbus-usa.com www.embedded-pc.com Intel ® Pentium ® M Processor embedded SBCs for demanding environments -30°C Power On 12 to 36 watts - for fanless sealed system design Two Philips 7130 for PAL/NTSC input For full specifications go to our website www.embedded-pc.com Microbus B e t t e r b y d e s i g n
Page 3 and 4: Editorial Editor: Dick Selwood E-ma
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Page 7 and 8: “The QNX Neutrino microkernel OS
Page 9 and 10: AEC-6810 Perfect Factory/Building A
Page 11 and 12: obust signal analysis. The mixed-si
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Page 15 and 16: See us at Embedded World 2006 Nurem
Page 18 and 19: ESE Magazine Jan/Feb 06 18 MOST -
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Page 33 and 34: Come learn how Microsoft embedded o
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Page 43 and 44: NO SLOWING DOWN. EVER. The market w
Page 45 and 46: Why use an RTOS? Tomoyuki Uda, Man
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