Rainbow Electronics AT45DB021E - Manual (Page 25)

25 AT45DB021E [PRELIMINARY DATASHEET]
8789B–DFLASH–11/2012
9. Additional Commands
9.1 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 will begin when the CS pin transitions from
a low to a high state. During the page transfer time (t
XFR
), the RDY/BUSY bit in the Status Register can be read to
determine whether or not the transfer has been completed.
9.2 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 will be compared with the data
bytes in the Buffer. During the compare time (t
COMP
), the RDY/BUSY bit in the Status Register will indicate that the part is
busy. On completion of the compare operation, bit 6 of the Status Register will be updated with the result of the compare.
9.3 Auto Page Rewrite
This command only needs to be used if the possibility exists that static (non-changing) data may be stored in a page or
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 may 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 20,000 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 1-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
will first transfer data from the page in main memory to the Buffer and then program the data from the Buffer back into
same page of main memory. The operation is internally self-timed and should take place in a maximum time of t
EP
.
During this time, the RDY/BUSY Status Register will indicate that the part is busy.