2

AT25SF321

DS-25SF321–047F–8/2017

Description

consumer based applications in which program code is shadowed from Flash memory into embedded or external RAM

for execution. The flexible erase architecture of the AT25SF321 is ideal for data storage as well, eliminating the need for

additional data storage devices.

The erase block sizes of the AT25SF321 have been optimized to meet the needs of today's code and data storage

applications. By optimizing the size of the erase blocks, the memory space can be used much more efficiently. Because

certain code modules and data storage segments must reside by themselves in their own erase regions, the wasted and

unused memory space that occurs with large block erase Flash memory devices can be greatly reduced. This increased

memory space efficiency allows additional code routines and data storage segments to be added while still maintaining

the same overall device density.

The device also contains three pages of Security Register that can be used for purposes such as unique device

serialization, system-level Electronic Serial Number (ESN) storage, locked key storage, etc. These Security Register

pages can be individually locked.

1.

Pin Descriptions and Pinouts

Table 1-1.

Pin Descriptions

Symbol

Name and Function

Asserted

State

Type

CS

CHIP SELECT: Asserting the CS pin selects the device. When the CS pin is deasserted, the

device will be deselected and normally be placed in standby mode (not Deep Power-Down

mode), and the SO pin will be in a high-impedance state. When the device is deselected,

data will not be accepted on the SI pin.

A high-to-low transition on the CS pin is required to start an operation, and a low-to-high

transition is required to end an operation. When ending an internally self-timed operation

such as a program or erase cycle, the device will not enter the standby mode until the

completion of the operation.

Low

Input

SCK

SERIAL CLOCK: This pin is used to provide a clock to the device and is used to control the

flow of data to and from the device. Command, address, and input data present on the SI pin

is always latched in on the rising edge of SCK, while output data on the SO pin is always

clocked out on the falling edge of SCK.

-

Input

SERIAL INPUT: The SI pin is used to shift data into the device. The SI pin is used for all data

input including command and address sequences. Data on the SI pin is always latched in on

the rising edge of SCK.

With the Dual-Output and Quad-Output Read commands, the SI Pin becomes an output pin

in on every falling edge of SCK

the SI pin unless specifically addressing the Dual-I/O and Quad-I/O modes in which case it

Data present on the SI pin will be ignored whenever the device is deselected (CS is

deasserted).

-

Input/Output