STMicroelectronics has announced a new family of 32-bit Flash Microcontrollers based on the ARM Cortex-M3 core - a core with features specifically designed for embedded applications requiring a combination of high performance (1,25 Dhrystone MIPS/MHz), low power and low cost.
Designed to deliver impressive levels of performance and energy efficiency while retaining all the benefits of working with the open, industry-standard ARM architecture and development environment, the STM32 is offered in two lines: the STM32F103 'Performance' line, with 72 MHz clock frequency, provides what the manufacturer claims is best-in-class 32-bit MCU performance, while the STM32F101 'Access' line, with 36 MHz clock frequency, offers users of 16-bit devices a significant increase in performance at the same 16-bit price levels. Both lines offer from 32 K to 128 K of embedded Flash memory but differ in maximum SRAM size and peripheral combinations. At 72 MHz, executing from Flash, the STM32 consumes only 36 mA, corresponding to an impressive 0,5 mA/MHz.
The Cortex-M3 core was specifically developed to target the low-cost requirements of a broad range of markets and applications where memory and processor size significantly impact device costs. Its enhanced integrated features include a nested vector-interrupt controller with down to six CPU cycles inter-interrupt latency, atomic bit manipulation allowing individual bits to be modified in a single write operation, branch speculation, single-cycle multiply, hardware divide, and the highly efficient Thumb 2 instruction set, leading to superior performance, code density, realtime behaviour, and power consumption.
Ideal for battery-operated applications, the STM32 operates from a 2,0 to 3,6 V power supply and has a power consumption down to 2 μA in standby mode with reset circuitry active. Other power-saving features include an integrated RTC with a dedicated pin for battery operation and a dedicated 32 kHz oscillator, and four low power modes.
In performance terms, the company claims that the STM32 family offers up to 30% faster processing than an equivalent ARM7TDMI-based product, or, for the same processing power, STM32 devices require 75% less power. Similarly, the Thumb 2 instruction set of the new core allows designers to reduce code size by up to 45%, almost halving the amount of memory they need to hold their applications. In addition, Dhrystones and other benchmarks show that the STM32 delivers at least twice the performance of the best 16-bit architectures.
The peripheral set includes up to 128 KB embedded Flash, up to 20 KB of RAM, up to two ADCs (12-bit at 1 μA conversion time), up to three USARTs; up to two SPI (18 MHz master/slave); up to two I²C; up to three 16-bit timers (four input capture/four output compare/four PWM each) and a dedicated 6-PWM timer with embedded dead times for regulation and motor control vector drive applications, as well as USB, CAN, and seven DMA channels. Embedded reset circuitry includes Power-On reset, Power-Down reset and Voltage supervisor, an embedded accurate 8 MHz RC factory-trimmed oscillator that can be used as the main oscillator, an embedded 4-16 MHz oscillator for external crystal, and dual watchdogs. As a result of this high integration level, only seven capacitors are needed (in addition to a power supply) for LQFP100 packaged devices.
In addition to traditional applications, such as industrial PLCs, domestic appliances, domestic and industrial security, fire and HVAC systems, and consumer/PC applications such as card readers and biometrics, the new STM32 family is particularly well-suited for portable applications such as glucose and cholesterol monitors where low power consumption is important.
Both STM32 lines are offered in LQFP48, LQFP64, LQFP100 and BGA100 packages, with 32, 64, and 128 K embedded flash options.
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