Rainbow Electronics AT45DB642 - Manual (Page 27)

27 AT45DB321E [PRELIMINARY DATASHEET]
8784B–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 either Buffer 1 or Buffer 2. To transfer a page of data using
the standard DataFlash page size (528 bytes), an opcode of 53h for Buffer 1 or 55h for Buffer 2 must be clocked into the
device followed by three address bytes comprised of one dummy bit, 13 page address bits (PA12 - PA0) which specify
the page in main memory to be transferred, and 10 dummy bits. To transfer a page of data using the binary page size
(512 bytes), an opcode of 53h for Buffer 1 and 55h for Buffer 2 must be clocked into the device followed by three address
bytes comprised of two dummy bits, 13 page address bits (A21 - A9) which specify the page in the main memory to be
transferred, and nine 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 Buffer 1 or Buffer 2 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 (528 bytes), an opcode of 60h for Buffer 1 or 61h for Buffer 2 must be clocked into the
device followed by three address bytes comprised of one dummy bit, 13 page address bits (PA12 - PA0) which specify
the page in the main memory to be compared to the buffer, and 10 dummy bits. To compare a page of data with the
binary page size (512 bytes), an opcode of 60h for Buffer 1 or 61h for Buffer 2 must be clocked into the device followed
by three address bytes comprised of two dummy bits, 13 page address bits (A21 - A9) which specify the page in the main
memory to be compared to the buffer, and nine 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 Buffer 1 or Buffer 2. 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 Buffer 1 or Buffer 2 and then the same data (from Buffer 1 or Buffer 2) 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 (528 bytes), a 1-byte opcode, 58H for Buffer 1 or
59H for Buffer 2, must be clocked into the device followed by three address bytes comprised of one dummy bit, 13 page
address bits (PA12-PA0) that specify the page in main memory to be rewritten, and 10 dummy bits.
To initiate an Auto Page Rewrite with the a binary page size (512 bytes), the opcode 58H for Buffer 1 or 59H for Buffer 2,
must be clocked into the device followed by three address bytes consisting of two dummy bits, 13 page address bits
(A21 - A9) that specify the page in the main memory that is to be rewritten, and nine 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 a buffer and then