AT45DB021E datasheet(31/74 Pages) DIALOG

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AT45DB021E

DS-AT45DB021E—8789J—03/2021

Additional Commands

10.1 Main Memory Page to Buffer Transfer

A page of data can be transferred from the main memory to the Buffer. To transfer a page of data using the

standard DataFlash page size (264 bytes), an opcode of 53h must be clocked into the device followed by three

address bytes comprised of five dummy bits, 10 page address bits (PA9 - PA0) which specify the page in main

memory to be transferred, and nine dummy bits. To transfer a page of data using the binary page size (256 bytes),

an opcode of 53h must be clocked into the device followed by three address bytes comprised of six dummy bits, 10

page address bits (A17 - A8) which specify the page in the main memory to be transferred, and eight dummy bits.

The CS pin must be low while toggling the SCK pin to load the opcode and the three address bytes from the input

pin (SI). The transfer of the page of data from the main memory to the Buffer begins when the CS pin transitions

from a low to a high state. During the page transfer time (tXFR), the RDY/BUSY bit in the Status Register can be

read to determine whether or not the transfer has been completed.

10.2 Main Memory Page to Buffer Compare

A page of data in main memory can be compared to the data in the Buffer as a method to ensure that data was

successfully programmed after a Buffer to Main Memory Page Program command. To compare a page of data with

the standard DataFlash page size (264 bytes), an opcode of 60h must be clocked into the device followed by three

address bytes comprised of five dummy bits, 10 page address bits (PA9 - PA0) which specify the page in the main

memory to be compared to the Buffer, and nine dummy bits. To compare a page of data with the binary page size

(256 bytes), an opcode of 60h must be clocked into the device followed by three address bytes comprised of six

dummy bits, 10 page address bits (A17 - A8) which specify the page in the main memory to be compared to the

Buffer, and eight dummy bits.

The CS pin must be low while toggling the SCK pin to load the opcode and the address bytes from the input pin

(SI). On the low-to-high transition of the CS pin, the data bytes in the selected Main Memory Page are compared

with the data bytes in the Buffer. During the compare time (tCOMP), the RDY/BUSY bit in the Status Register

indicates that the part is busy. After the compare operation, bit 6 of the Status Register is updated with the result of

the compare.

10.3 Auto Page Rewrite

This command must be used only if the possibility exists that static (non-changing) data are stored in one or more

pages of a sector and the other pages of the same sector are erased and programmed a large number of times.

Applications that modify data in a random fashion within a sector can fall into this category. To preserve data

integrity of a sector, each page within a sector must be updated/rewritten at least once within every 50,000

cumulative page erase/program operations within that sector. The Auto Page Rewrite command provides a simple

and efficient method to “refresh” a page in the main memory array in a single operation.

The Auto Page Rewrite command is a combination of the Main Memory Page to Buffer Transfer and Buffer to Main

Memory Page Program with Built-In Erase commands. With the Auto Page Rewrite command, a page of data is

first transferred from the main memory to the Buffer and then the same data is programmed back into the same

page of main memory, essentially “refreshing” the contents of that page. To start the Auto Page Rewrite operation

with the standard DataFlash page size (264 bytes), a one-byte opcode, 58h must be clocked into the device

followed by three address bytes comprised of five dummy bits, 10 page address bits (PA9-PA0) that specify the

page in main memory to be rewritten, and nine dummy bits.

To initiate an Auto Page Rewrite with the a binary page size (256 bytes), the opcode 58h must be clocked into the

device followed by three address bytes consisting of six dummy bits, 10 page address bits (A17 - A8) that specify

the page in the main memory that is to be rewritten, and eight dummy bits. When a low-to-high transition occurs on

the CS pin, the part first transfers data from the page in main memory to the Buffer and then programs the data

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