6

AT25FS040

5107D–SFLSH–09/06

Power On Reset

Protection

In order to prevent data corruption and inadvertent write operations during device

power-up and power down, a Power On Reset (POR) circuit is enabled. At Power-up

(continuous rise of Vcc from 0v), the device will not respond to any instruction and will

be held in reset (which puts the device in standby mode) until the Vcc has reached the

Power On Reset threshold voltage. This threshold is lower than the minimum specified

Vcc operating voltage.

At power down (continuous fall of Vcc), when Vcc drops from the operating voltage

below the POR threshold, all operations are disabled and the device will not respond to

any command. A stable and valid Vcc must be applied before executing any communi-

cation. Please note: The POR threshold trip point is ~1.8V for Serial Flash products and

is ensured by design to have a reset during power-up and power down and is not 100%

tested.

Figure 2. SPI Serial Interface

MASTER:

MICROCONTROLLER

SLAVE:

AT25FS040

DATA OUT (MOSI)

DATA IN (MISO)

SERIAL CLOCK (SPI CK)

SS0

SS1

SS2

SS3

SI

SO

SCK

CS

SI

SO

SCK

CS

SI

SO

SCK

CS

SI

SO

SCK

CS