ARM9 microcontroller sports connectivity, large on-chip memory
By Robert Cravotta, Technical Editor -- EDN, May 9, 2006
STMicroelectronics’ STR910F series of ARM9E-based microcontrollers combine Ethernet, CAN (controller-area-network) 2.0B, USB-FS support; as much as 96 kbytes of SRAM; and as much as 544 kbytes of flash in a single device. The ARM9E core includes single-cycle DSP instructions that can take advantage of simultaneous access of code and data. The core operates at 1.8V±10%, and the I/O ring operates at 2.7 to 3.6V. The burst flash supports a minimum of 100,000 erase cycles with 20-year data retention, and it can support a peak execution performance of 96 MHz.
The Ethernet MAC (media-access controller) includes an MII (media-independent interface) to an external PHY (physical) layer, and the dedicated Ethernet DMA controller can support the movement of 91 Mbps of raw Ethernet frames between the MAC and the SRAM while loading the CPU by 10%. Other peripherals include an eight-channel, 10-bit ADC; a three-phase ac-motor-control unit; supervisor functions with low-voltage-reset and brownout detect, real-time clock, and as many as 80 5V-tolerant I/O pins.
Access to the SRAM by the core and peripherals is through an alternating arbiter that guarantees a deterministic direct path to the SRAM. The real-time clock draws less than 1 μA across the entire temperature range. It can record the time of a tamper event and cut power to the SRAM to destroy contents if desired; external real-time clock devices costing 50 cents to $1 each typically support these features. Power consumption of the core ranges from 1.3 mA per megahertz in run mode to 55 μA in sleep mode, in which the device is quiescent with the real-time clock running. Battery current when the main power is off with only the real-time clock operating is as low as 0.3 µA at room temperature and 0.9 µA maximum, and it is 5 µA at room temperature and 85 μA maximum when the SRAM is also alive.
Six STR910F devices are available now in lead-free packages with pricing starting at $6.99 (10,000). The LQFP80 and LQFP128 packages support operation over a temperature range of –40 to +85 degrees Celsius. The LQFP128 packages include an Ethernet MII and an external-memory-bus interface. Starter kits are available from Hitex (www.hitex.com), IAR Systems (www.iar.com), Keil Software (www.keil.com), and Raisonance (www.raisonance.com) for as low as $199. These kits include free compilers that are code-limited to either 16 or 32 kbytes. The kits also include JTAG debugging, programming cable, code examples, and hardware to begin a design.
STMicroelectronics’ STR910-Eval evaluation board allows designers to exercise and evaluate all of the hardware interfaces and I/O of the STR910F for $249. Designers can use the included demonstration code for the Ethernet, USB, CAN, and the other major chip functions based on a common HAL (hardware-abstraction-layer) library. STMicroelectronics’ free CAPS (configuration-and-programming-software) tool allows developers to configure I/O-pin and clock functions using a graphical interface. The tool automatically generates a C header file that reflects the developer’s pin and clock choices. RTOS and TCP/IP support are available from CMX (www.cmx.com), Micrium (www.micrium.com), Segger (www.segger.com), Keil, and NexGen Software (www.nexgen-software.fr).
