The AT45DB021B is a 2.7-volt only, serial interface Flash memory ideally suited for a wide variety of digital voice, image, program code and data-storage applications. Its 2,162,688 bits of memory are organized as 1024 pages of 264 bytes each. In addition to the main memory, the AT45DB021B also contains two SRAM data buffers of 264 bytes each. The buffers allow receiving of data while a page in the main memory is being reprogrammed, as well as reading or writing a continuous data stream.
EEPROM emulation (bit or byte alterability) is easily handled with a self-contained three step Read-Modify-Write operation. Unlike conventional Flash memories that are accessed randomly with multiple address lines and a parallel inter-face, the DataFlash uses a SPI serial interface to sequentially access its data. DataFlash supports SPI mode 0 and mode 3. The simple serial interface facilitates hardware layout, increases system reliability, minimizes switching noise, and reduces package size and active pin count. The device is optimized for use in many commer-cial and industrial applications where high density, low pin count, low voltage, and low power are essential. The device operates at clock frequencies up to 20 MHz with a typical active read current consumption of 4 mA.
To allow for simple in-system reprogrammability, the AT45DB021B does not require high input voltages for programming. The device operates from a single power supply, 2.7V to 3.6V, for both the program and read operations. The AT45DB021B is enabled through the chip select pin (CS ) and accessed via a three-wire interface consisting of the Serial Input (SI), Serial Output (SO), and the Serial Clock (SCK).
All programming cycles are self-timed, and no separate erase cycle is required before programming.
When the device is shipped from Atmel, the most significant page of the memory array may not be erased. In other words, the contents of the last page may not be filled with FFH.