AT45DB321C datasheet(15/37 Pages) ATMEL

15 / 37 page

AT45DB321C [Preliminary]

3387B–DFLSH–9/04

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 instruc-

tion. 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 mini-

mum 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 mini-

mum distance or appropriately terminated 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 capa-

bility. 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 programming 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 6.

It is recommended that the RDY/BUSY bit of status register or the RDY/BUSY pin be

monitored in order to minimize the erase and programming time.

Atmel C generation DataFlash utilizes a sophisticated adaptive algorithm during erase

and programming 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 pro-

grammed successfully. If the memory cells were not erased or programmed, the

algorithm loops back and erases or programs the memory cells again. The process will

continue until the device is erased or programmed successfully.

The erase and programming operations are internally self-timed and fixed timing is not

recommended.

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