Freescale: Thin-film flash mimics EEPROM

PORTLAND, Ore. —Freescale Tuesday (March 2) unveiled its 90-nanometer thin-film flash memory technology for next-generation microcontrollers at Embedded World tradeshow in Nuremburg, Germany. The thin-film flash memory technology is set to be delivered on microcontrollers in the second half of the year, according to Freescale.

Freescale unveiled its FlexMemory scheme for microcontrollers, said to make life easier for applications programmers. The FlexMemory approach surrounds flash memory with a hardware architecture that simplifies tasks for programmers by emulating ordinary electrically erasable programmable read only memory (EEPROM), according to Freescale.

"One of the key things that FlexMemory enables us to do is to treat flash memory as if it were a standard EEPROM," said Jeff Bock, global marketing manager for industrial and multi-market microcontrollers. "FlexMemory gives you very fast access times, byte-level read while writes, and programmable endurance up to 10 million cycles."

Freescale described how it was moving from polysilicon floating gates for its embedded flash to nanocrystalline thin-film floating gates last year. The advantage of Freescale's thin-film storage material is that it is relatively immune to leakage, since charge is isolated on nanocrystals thereby preventing any single defect from draining charge off the whole floating gate.

Today, original equipment manufacturers (OEMs) must roll-their-own software to make flash memory—which can only be written and erased in large blocks—appear to be capable of ordinary byte-level writes and erase like a traditional EEPROM. By mapping virtual EEPROM onto flash memory blocks, an algorithm can emulate byte-level writes by re-writing the whole block into a new location along with the single changed byte. To speed up that lengthy process, OEMs must add SRAM buffers plus the memory management software with which application must interface.

Freescale stores its floating gates on a thin film layer (left) where nanocystalline charge domains are too small (about 100 angstroms, right) to leak off.

FlexMemory, on the other hand, combines SRAM, flash, and on-chip firmware to handle all the complexities of EEPROM emulation in a manner that is transparent to applications. OEMs program FlexMemory to trade-off flash memory size for endurance—the smaller the size the longer the endurance, and the larger the size the shorter its endurance. FlexMemory can also be configured by the OEM as plain old flash memory or as a combination of EEPROM and flash memory. Either way, Freescale claims OEMs using its hardware implementation of FlexMemory will gain a 10-times improvement in performance.

Freescale said its FlexMemory-based microcontrollers are aimed at consumer electronics, household appliances, medical devices, smart metering systems and similar applications.