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MCU combines SRAM, flash

Posted: 10 May 2006 ?? ?Print Version ?Bookmark and Share

Keywords:STR910F? flash microcontroller? Ethernet? ARM9E? processor core?

STR910F flash MCUs

STMicroelectronics introduced the STR910F flash microcontroller family, which combines Ethernet connectivity, an ARM9E processor core, and embedded SRAM and flash memories. The STR910F series was developed to meet the growing demand for embedded-control applications and to enable Ethernet connectivity.

STR910F devices employ an ARM966E-S core that accesses its instruction and data memories using two separate internal busses. Each of these memories is attached to the core through a tightly-coupled memory (TCM) interface. The STR910F places a high-speed burst flash memory on the instruction TCM and a zero-latency SRAM on the data TCM. The result, according to STMicro, is 96MIPS peak code execution at 96MHz.

Instead of a memory management unit with cache, the STR910F supports a simple memory model well-suited for compact real-time operating systems (RTOS). It also uses a memory accelerator with a pre-fetch queue and branch-cache system to boost performance during non-sequential code execution from burst flash memory.

According to STMicro, the product family was given large memories to support the use of RTOS and TCP/IP stacks. SRAM sizes range up to 96Kbytes. This SRAM can be protected by a battery or super-capacitor connected to the battery input pin, and optionally the SRAM contents can be automatically destroyed for secure applications in response to a signal on the STR910F's tamper-detection input pin. Flash memory sizes range up to 544Kbytes, and is configured into dual banks of read-while-write memory. Each of the SRAM and flash memories may be used for either instructions or data.

The STR910F has up to nine DMA channels to support high-speed communication channels, making data movement between peripherals and memory almost transparent to the CPU, freeing the CPU to perform real-time control tasks. These DMA controllers allow peripherals on the Advanced High-performance Bus and Advanced Peripheral Bus to act as a master to the SRAM, sharing SRAM access with the CPU through an arbitrator for streamlined data flow.

In addition to its Ethernet media access controller, the MCU series support peripherals including USB Full Speed, CAN, three UART/IrDA, two SPI, two I2C, eight-channel 10bit ADC, four 16bit timers, a three-phase AC motor control unit, supervisor functions with low voltage reset and brownout detect, a real-time clock, an external memory interface, an ETM9 debug and trace interface, and up to 80 5V tolerant I/O.

The product family's power consumption can be dynamically adjusted, giving the CPU the ability to gate and scale the system and peripheral clocks, including a sleep mode drawing 55A, typical. When main power to the device is shut off or is absent because of a fault, the STR910F will automatically switch to the battery supply pin to keep the real-time clock active. The embedded real-time clock has full calendar and alarm functions, and draws less than 1A on the battery supply pin across the -40C to 85C temperature range.

Starting mid-May 2006, STR910F users will get support from STMicro and third parties, with starter kits at $199. Kits include a compiler and debugger (limited code size), a JTAG debugging and programming cable, code examples, and necessary hardware to begin a design. STMicro provides an evaluation board, the STR910-EVAL, at $249. To assist in configuring the STR910F's I/O matrix and clock functions, ST offers Configuration and Programming Software (CAPS), a free tool used to choose pin functions and clock distribution. CAPS automatically generates a C header file that reflects the entire pin and clock choices. RTOS and TCP/IP support will be available mid-May.

Six part numbers are offered, all in lead-free packages. Devices are packaged as LQFP80 and LQFP128, with the LQFP128 packages offering the Ethernet Media Independent Interface and the external memory bus interface. SRAM ranges from 64Kbytes to 96Kbytes and flash memory ranges from 288Kbytes to 544Kbytes. The core operates at 1.8V 10 percent, and the I/O ring at 2.7V to 3.6V, over a temperature range of -40C to 85C.

STR910F devices are available from May 2006, with pricing for the series starting at $6.99 for quantities of 10,000.

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