AT45DB321C datasheet(17/40 Pages) ATMEL

17 / 40 page

3387L–DFLASH–6/06

AT45DB321C

Power-on/Reset State

When power is first applied to the device, or when recovering from a reset condition, the device

will default to Mode 3. In addition, the output pin (SO) will be in a high impedance state, and a

high-to-low transition on the CS pin will be required to start a valid instruction. The mode (Mode

3 or Mode 0) will be automatically selected on every falling edge of CS by sampling the inactive

clock state. After power is applied and V

CC is at the minimum datasheet value, the system

should wait 20 ms before an operational mode (DataFlash) is started.

System Considerations

The RapidS serial interface is controlled by the serial clock SCK, serial input SI and chip select

CS pins. These signals must rise and fall monotonically and be free from noise. Excessive noise

or ringing on these pins can be misinterpreted as multiple edges and cause improper operation

of the device. The PC board traces must be kept to a minimum distance or appropriately termi-

nated to ensure proper operation. If necessary, decoupling capacitors can be added on these

pins to provide filtering against noise glitches.

As system complexity continues to increase, voltage regulation is becoming more important.

A key element of any voltage regulation scheme is its current sourcing capability. Like all Flash

memories, the peak current for DataFlash occur during the programming and erase operation.

The regulator needs to supply this peak current requirement. An under specified regulator can

cause current starvation. Besides increasing system noise, current starvation during program-

ming or erase can lead to improper operation and possible data corruption.

For applications that require random modifications of data within a sector, please refer to “Auto

Page Rewrite” on page 8.

Atmel C generation DataFlash utilizes a sophisticated adaptive algorithm during erase and pro-

gramming to maximize the endurance over the life of the device. The algorithm uses a

verification mechanism to check if the memory cells have been erased or programmed success-

fully. If the memory cells were not erased or programmed completely, the algorithm erases or

programs the memory cells again. The process will continue until the device is erased or pro-

grammed successfully.

In order to optimize the erase and programming time, fixed timing should not be used.

Instead, the RDY/BUSY bit of the status register or the RDY/BUSY pin should be

monitored.

AT45DB321C 데이터시트(PDF) 17 Page - ATMEL Corporation