Texas Instruments Inc. has expanded its Stellaris portfolio with 40 devices in the LM4Fx family which are the first Cortex-M-based microcontrollers to be built on 65 nanometer technology.
The devices have a ARM Cortex-M4F floating-point core operating at up to 80 MHz and two 12-bit analog-to-digital converters (ADCs) and three comparators to support mixed-signal applications.
The MCUs provide 12-bit ADC accuracy at the full 1 MSPS rating without any hardware averaging, eliminating any performance tradeoffs and have standby currents down to 1.6 µA. The ADCs can generate processor interrupts based on a conversion completion as well as on a match to one of eight digital comparators. Readings from the ADCs can be queued, compared and averaged within the ADC. The on-chip micro direct memory access controller (μDMA) can feed ADC readings from the ADC FIFOs to RAM or another peripheral without waking up or distracting the ARM core.
There are also three on-chip analog comparators that can be used with a programmable internal voltage reference detect when an input analog signal has crossed a specific threshold. These three analog comparators, along with the digital comparators, remove the requirement of continuously polling incoming ADC values and free up the CPU to focus on real-time application tasks.
Connectivity options including USB (host, device and On-The-Go), UARTs, I2C, SSI/SPI and CAN to support communications while integrated EEPROM supports high-endurance non-volatile storage of user interface or configuration parameters to reduce system cost.
The family provide options for up to 256KB flash and 32KB SRAM to address varying application needs.
Previous Stellaris generations used the original Cortex-M3 architecture. The Thumb-2 instruction set of this earlier version of the Cortex-M core is a high-density, power-efficient instruction set suitable for a variety of general-purpose data processing and control operations.
The Cortex-M3 Thumb-2 instructions include arithmetic, logical, bit, branch and data movement operations found on many MCUs.
The Cortex-M4 expands the instruction offering of the Cortex-M3 by adding digital signal processing extensions and single instruction, multiple data (SIMD) instructions. The Stellaris LM4F series also includes the floating point option (the “F” in the Cortex-M4F) across the entire offering of LM4F products.
The DSP operations of the Stellaris LM4F series include single-cycle 32-bit or dual 16-bit multiply-accu- mulate (MAC) instructions and saturating arithmetic instructions. Optimized SIMD instructions can perform four 8-bit or two 16-bit arithmetic operations in a single cycle and are therefore very effective at performing arithmetic operations on large arrays of data. The hardware divide logic produces a result in between 2 and 12 clock cycles. Together, these instructions add DSP-like capability to a responsive controller core.
The single precision floating-point instructions are compliant with the IEEE 754 standard and include functions such as square root and a fused MAC that enable higher precision. Numerous data type conver- sions are available, speeding transitions between domains.
Stellaris LM4F MCUs have a number of clock and power domains that can be gated as needed to manage power. When the DSP or floating-point units are not needed, for example, or if any of the peripherals will be idle, power and/or clocking to those modules can be shut down in order to optimize power consumption.
The devices provide sleep, deep-sleep and hibernate modes to save power when minimal functionality is required. In the hibernate mode, power to the entire chip is cut off except to the HIB block, leaving the MCU in a state where it can be brought back to life when the need arises. The HIB block includes a 32 kHz oscillator circuit, a supporting real-time clock (RTC) module, a battery monitor circuit and sixteen 32-bit words of backup battery SRAM. This minimalist implementation allows the power consumption to be reduced, in hibernate mode, to as little as 1.6 μA. The Stellaris LM4F devices can be awakened from hibernation by an RTC match, from an external signal, or from a low voltage detection circuit.
The free license and royalty-free StellarisWare software enables all programming can be in C/C++, even interrupt service routines & startup code. It includes hundreds of example projects, application and peripheral libraries and open source stacks. To conserve flash memory, TI also offers the software pre-loaded in ROM.
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Supported by five popular IDEs, Stellaris microcontroller kits jumpstart design in 10 minutes or less. Developers can easily scale designs and reuse code across the entire code compatible Stellaris Cortex-M microcontroller platform.
The Stellaris EKS-LM4F232 USB+CAN evaluation kit for Code Composer Studio features a MCU in a 144-LQFP package, USB OTG connector, a microSD card slot, a coin cell battery for use with the Stellaris low-power Hibernate mode, a temperature sensor, a three-axis accelerometer for motion detection, and easy access through holes to all of the available device signals. This is the first kit to include a color OLED display.
The Stellaris Cortex-M4F microcontrollers start at $1.53 at 10K quantities. The EK-LM4F232 evaluation kit is priced at $149.