San Jose, Calif. Atmel Corp.'s three newest additions to its SAM7 family of ARM7-based USB microcontrollers offer flash memory densities of 32-, 256-, and 512-Kbytes. The SAM7SE MCUs are said to be the only ARM7-based units to include an external bus interface (EBI) that provides access to massive amounts of external NAND Flash, SDRAM, CompactFlash, SRAM and ROM storage. The ability to efficiently store and retrieve over a gigabyte of data makes SAM7SE MCUs ideal for data logging applications such as ambulatory medical monitoring.
The EBI on the AT91SAM7SE MCUs supports 32-bit NAND Flash, SDRAM and CompactFlash memories in TrueIDE mode. It includes a NAND Flash controller with a complementary error-correcting code controller (ECC) that compensates for bits that are lost by NAND flash memory over time. A built-in memory controller offers up to eight configurable chip selects and supports a wide range of 16- and 32-bit static devices including SRAM, ROM, Flash, memory mapped LCD and FPGA.
Data logging applications have usually been implemented with costly, power-hungry ARM9-based microcontrollers because they were the only MCUs available that supported SDRAM and NAND Flash memories. Conventional ARM7 MCUs require intensive bit manipulation through the general purpose I/O in these applications which significantly reduces the available processing power. With the SAM7E family, designers can now use these smaller-footprint, ARM7-based MCUs to implement battery-powered, portable versions of these applications.
A major problem when external memory or logic is used is that it makes the on-chip flash vulnerable to external, potentially unauthorized, access. Atmel's SAM7E microcontrollers have several features that secure the code. Among them is the MCU cannot boot from external memory. A Flash security bit disables the Fast Flash Programming Interface (FFPI) and JTAG access to the on-chip Flash memory. In addition, a memory protection unit (MPU) can be configured to enforce code execution from on-chip Flash, thereby preventing execution from an outside source.
Dual-bank memory on 512 KB MCU supports enhanced in-application programming. Dual-bank Flash memory on the 512 KByte SAM7SE allows true read-while-write capability so systems can be reprogrammed while continuing to operate. The dual-bank memory also protects the system from power failures or other errors that can cause an unrecoverable system failure.
Modern communications protocols have maximum data rates that conventional ARM7 MCUs cannot support. For example full-speed USB operates at 12 Mbps and high-speed SPI operates at 25 Mbps. At only 4 Mbps, conventional ARM7s become so bogged down that they cannot effectively process data. Like Atmel's other SAM7 MCUs, the SAM7SE-series has an11-channel peripheral DMA controller (PDC) that increases on-chip bandwidth to 10 Mbps while maintaining 96% of the CPU's cycles for application processing. The PDC can store the streaming content directly in the external NAND Flash or SDRAM without CPU intervention.
Peripherals support real-time deterministic applications. The SAM7SE-series includes the same supervisory features found on 8-bit MCUs including a brown-out detector, power-on- reset, real-time clock, crystal oscillator, watchdog timer and three 16-bit timers. Communication interfaces include three USARTs, USB, TWI, I2S (SSC) and SPI. The device also has four pulse width modulators, an 8-channel, 10-bit analog-to-digital controller and 88 I/O pins.
Three PIO controllers allow simultaneous peripheral access. Traditional MCUs multiplex the peripherals, frequently creating a bottleneck when there are multiple peripheral accesses. Three individual PIO controllers avoid this problem. When the EBI is not in use, all peripherals can be accessed simultaneously.
The AT91SAM7SE512 is available now in 128 pin Green QFP or BGA packages and priced at $8.43 and $9.38, respectively, in quantities of 10,000. The AT91SAM7SE256 and AT91SAM7SE32 will be available in early 2007.
For further information on Atmel's AT91SAM Smart ARM-based Microcontrollers, go to
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