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What is underneath the bonnet of TI's latest processors that makes them 'industrial ready'?

Having embraced the industrial market with its Sitara AM335x range of processors – a range that included the 1GHz, 2000MIPS AM3358, which is at the heart of the BeagleBone Black development platform – Texas Instruments (TI) has tailored its latest family, the Sitara AM437x, to further suit industrial demands.

One key aspect of this is support for the main industrial protocols including EtherCAT, EtherNET/IP, Profibus, PROFINET – RT/IRT, Sercos III and IEC61850, with motor feedback protocols like EnDat and interfaces for sensors and actuators like BiSS also supported. The devices are hardware ready for all of these protocols with the necessary firmware subsequently loaded to implement the desired ones. There can now be two protocols per device.

These protocols are loaded onto the PRU-ICSS, which stands for programmable real time unit industrial communication sub systems. TI's EMEA industrial system applications manager Elizabete de Freitas said the PRUs can equally provide the flexibility for programming with proprietary protocols or other additional features that can further differentiate and innovate the application.

Moreover, it can instantly take a component out of the mix. De Freitas said: "Protocols such as EtherCAD and Profinet exist today either in the form of ASICs or as VHDL for different FPGAs. What we have here is the capability of implementing these protocols in the subsystem, replacing the need for external FPGAs. We have it implemented in an SoC that also features an ARM core and a variety of peripherals."

The 335x featured two PRU cores, enough to allow a single protocol to be loaded. The 437x family has gone a step further to suit target applications. De Freitas explained the rationale: "If you take a drive application, you might want an industrial communications protocol such as EtherCAT and a protocol that, for example, reads the position of the motor, such as EnDat 2.2. In the AM335, we would need two devices to implement that, but because the AM437 has four cores, we can do it in a single chip."

At the heart of the device is the ARM Cortex-A9, an upgrade from the Cortex-A8 used in the AM335 and one of the reasons why TI is claiming the AM437 provides a 40% improvement in system performance compared to the AM335, figures assessed without taking into account the power efficiency attributes of the A9.



Some of this system performance comes from the improved DMIPS rate of the A9, along with its floating point performance. "We combine those elements and then factor in speed to internal memory, the size of that internal memory and even the access to external memory and the speed of that," said de Freitas. "That will make up what we are calling the system performance."

The ARM Cortex-A9, which can run up to 1GHz, has its own internal 256kbyte memory and there is an additional 256kbyte of L3 memory – a significant improvement to the 64kbyte on the AM335. There is also a 32bit external memory interface; its predecessor had a 16bit port.

The additional performance the processor brings is supplemented by a rich peripheral set. While there are two camera interfaces, a new peripheral for this member of the Sitara family, other interfaces and peripherals are common with the AM335, such as six UARTS, SPI ports and USBs with PHY integrated.

Familiarity, said de Freitas, is something engineers appreciate. "I think it is important from a know-how point of view, but it is more important from a reuse point of view." She highlighted that software development played a significant part in overall development costs, and added: "When we can offer as much reuse as possible, it is always very welcome. Of course, it cannot be a 'me too' product; it has to be differentiated. But it has to be differentiated in areas that are critical. In other areas, by reusing developments, performance can be guaranteed."

The Sitara AM437x processors also contain a POWERVR SGX 3D graphics accelerator and a display subsystem that enables colour space conversion, overlays, resizing and more.

The initial evaluation module (EVM) has a Linux software development kit while, in the autumn, there will be further development kits targeted specifically at industrial applications with support for real time operating systems.

Also included in the EVM is a 7in capacitive touch LCD with a connector to plug in TI's WiLink8 combo connectivity modules. The WiLink 8 modules include software drivers that are integrated and tested with the standard Linux SDK. Customers can purchase the industrial development kit in Q3 of 2014. This will help in the development of industrial automation applications, including programmable logic controllers and drives.

There is already a 'home grown' RTOS for the AM335 which is supplied for industrial development kits. However, in relation to waiting until software support was available from TI's Developer network partners, de Freitas commented: "The decision of when to use a high level OS or an RTOS is often to do with the overall requirements for the end application. It has to do with latency requirement, which is related to how real time the real time system needs to be. Does the developer have legacy software that needs to be reused? What is the company's experience in various areas? A number of factors contribute to the decision of which software bases to use. Of course, we see Linux as a strong requirement, especially when we look at Human Machine Interface type applications."

The AM437 has a companion chip to manage its power requirements and this can also be used, in some cases, to manage power for other parts of the system. "We have integrated simplified power sequencing in the AM437x that we didn't have before," said de Freitas. "Therefore the external power management IC is actually simplified. The TP65218 is really there to provide DC/DC converters with integrated power path for the core voltage supervisors for the different I/Os in the system."

Power consumption, claims TI, can consequently be reduced by 70%, making it suitable for systems requiring a low capacity coin cell battery to support shelf life of greater than five years. The availability of quad SPI allows execute in place, so the system can run directly from low cost NOR flash.

De Freitas stressed that, while the AM437x has a role in IoT applications, it is not part of a family of cheap chip controllers. "We have recently bought out the CC3100 and CC3200, which have the capability of bringing WiFi to applications where it was not possible up to now because of the complexity and the price. We believe we are bringing a game changer to the market," de Freitas said, by way of demonstrating where Sitara devices sit in terms of IoT uses.

"The AM437x is aimed more at gateway type applications," she concluded. "A gateway that gathers several different types of sensor data before it connects to some cloud, for example, is a realistic use case."

Author
Tim Fryer

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