Date: 08/08/2012

ST's 32 bit ARM Cortex M offerings is built for price/performance

ST Microelectronics is offering wide range of MCU family based on ARM Cortex M processor cores which include M0, M3 and M4. The user is provided with broad choice on multiple parameters. Cortex M series are designed to offer low power consumption, easy programming and wide availability of 3rd party IDE tools. ST offering is designed for reliable and good performance but not rising the BOM cost. This writer gets some bytes of design hints from ST's MCU experts Bertrand Denis, 32-bit MCU Product Line Manager, Frank Martins, MCU Marketing Manager, Asia Region, and Vinay Thapliyal, Technical Marketing Manager (MCUs), ST India at recently held Embedded Systems Conference in Bangalore.

Standby power vs Active power vs low power consumption:
The importance really dependent on applications, The power consumption is important for both mains operated and battery operated applications, Let's take two examples, say per example applications requiring cell battery, in this one power consumption is key, because you don't even have recharge option, also you have constraints in terms of peak power consumption, where peak current of battery can source is limited. So this is very important and in that case standby mode, low power mode and active mode power consumption is important.

But there are some applications where the power supply is external but have a current limitation of say 20 milli Amperes, for these kind of applications its not a problem about low power mode but active mode is key.

You can find other applications such as battery recharged applications one thing which is now becoming very popular is GPS watch. GPS watch uses rechargeable battery. let's say your system has two modes. When it is off only the watch/time part working. In other mode you use the GPS. In this application low power mode is very important and active mode is not that important.

ST offers a sub-family called STM32L for designer for low power applications.

The SRAM size in a microcontrorller and the software code size:
Again it depends on applications. Its difficult for a programmer limit himself say 32Kb, that's why we offer big portfolio of choices. Even if the large SRAM size is available for programmer, a programmer still need to be cautious so that he can save resources. But the larger memory allows programmers to allow more features in the end product. So the demand for more features in end-product grows, the availability of SRAM size is also growing. This trend is expected to continue.

Moving from 8/16bit design to 32-bit:
The main problem of the designer in going from 8/16 bit 32 bit is fear. The 32 bit ARM Cortex M is built for easy development and that's why it's a big success in the market. Things are made easy for the designer. For assembly language experts moving from 8/16 bit to 32 bit makes less difference but when C is the language of choice for embedded system programmers 32-bit offers no disadvantage by the complexity of programming. So for a new user 32 bit is a better option.

Programming in higher language now is advantageous compared to lower language. Migration from one platform to other platform is easier.
Smart Phone

Picture: Frank Martins, Bertrand Denis, and Vinay Thapliyal (from L to R) holding less than US$8 priced (approx. Rupees 450) embedded board called STM32F0-Discovery. This board is available in volumes immediately.