Embedded systems designers may aspire to a single-chip solution to their problem, but rarely get very close to achieving it. Their chosen microcontroller may lack an essential interface or they may need to add custom logic to augment the functions they code on to the MCU.
And, interfaces to the real-world signals their design gathers from its sensors, and its outputs to drives or actuators, will demand analogue circuitry for signal-conditioning and power control.
Into this space, Actel has now introduced SmartFusion – a single-chip device that integrates an ARM Cortex-M3 microcontroller core, high-performance FPGA fabric developed from the company’s pASIC3 programmable logic technology, and configurable analog functions that use a high-voltage, high-speed technology.
The Cortex-M3 core is a 100 MHz (125 DMIPS) device with up to 512 KB of flash memory and 128 KB of SRAM. It is a ‘hard’ core – that it, it is diffused in the silicon in the most area-efficient implementation.
It is powerful enough to run complex algorithms, readily running precision motor control, or even multi-axial control of several motors, and comes with a peripheral set that includes 10/100 Ethernet MAC (media access controller) and other interfaces including SPI, I2C, UARTs and RS485.
Ample digital I/Os operate at up to 350 MHz, support I/O levels for interface standards such as LVDS, PCI and PCI-Express, and will drive up to 24 mA.
Mixed-signal I/O lines run at up to 180 MHz and drive up to 6 mA. FPGA resources comprise up to 500k gates and 108 KB of SRAM, in a flash-based fabric that supports up to 350MHz clock speeds. The flash technology yields programmable devices that are live at power-up, and secure; eliminating off-chip configuration memory removes a vulnerability to design copying. Designers can add further intellectual property protection by permanently disabling access to configuration memory after programming.
The silicon technology that builds on-chip flash, which requires elevated programming voltages, also enables high-voltage and high-performance analog functions.
SmartFusion chips will host up to three 12-bit successive-approximation (SAR) analog-digital converters (ADCs) that will run at up to 500 ksamples/sec at full resolution. Each ADC has a corresponding first-order, 1-bit sigma-delta DAC, with 5 sec refresh and 12-bit resolution. Analog functions are grouped within Signal Conditioning Blocks (SCBs) comprising, for example, accurate high-voltage and current monitors, temperature monitors and high-speed (50 nsec) comparators.
In the SCBs there are also bipolar scaling functions to condition captured signals. Labelled ABPSs, active bipolar pre-scalers, they have 1 MHz input bandwidth with 1 Mohm input impedance. Closely associated with the analog SCBs is the analog compute engine or ACE, a completely new, semi-autonomous block that carries out extensive analog pre- and post-processing, including sampling and sequencing of signal acquisition, without the intervention of the ARM processor.