Rainbow Electronics AT45DB041E - Manual (Page 28)

28 AT45DB041E [ADVANCE DATASHEET]
8783B–DFLASH–11/2012
To initiate an Auto Page Rewrite with the a binary page size (256 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 three dummy bits, 12 page address bits
(A20 - 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
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.
If a sector is programmed or reprogrammed sequentially page by page and the possibility does not exist that there will be
a page or pages of static data, then the programming algorithm shown in
Figure 26-1 on page 61 is recommended.
Otherwise, if there is a chance that there may be a page or pages of a sector that will contain static data, then the
programming algorithm shown in
Figure 26-2 on page 62 is recommended. Please contact Adesto for availability of
devices that are specified to exceed the 20,000 cycle cumulative limit.
Note: The Auto Page Rewrite command uses the same opcodes as the Read-Modify-Write command. If data
bytes are clocked into the device, then the device will perform a Read-Modify-Write operation. See the
Read-Modify-Write command description on
page 12 for more details.
9.4 Status Register Read
The 2-byte Status Register can be used to determine the device's ready/busy status, page size, a Main Memory Page to
Buffer Compare operation result, the sector protection status, Freeze Sector Lockdown status, erase/program error
status, Program/Erase Suspend status, and the device density. The Status Register can be read at any time, including
during an internally self-timed program or erase operation.
To read the Status Register, the CS pin must first be asserted and then the opcode D7h must be clocked into the device.
After the opcode has been clocked in, the device will begin outputting Status Register data on the SO pin during every
subsequent clock cycle. After the second byte of the Status Register has been clocked out, the sequence will repeat
itself, starting again with the first byte of the Status Register, as long as the CS pin remains asserted and the clock pin is
being pulsed. The data in the Status Register is constantly being updated, so each repeating sequence may output new
data. The RDY/BUSY status is available for both bytes of the Status Register and is updated for each byte.
Deasserting the CS pin will terminate the Status Register Read operation and put the SO pin into a high-impedance
state. The CS pin can be deasserted at any time and does not require that a full byte of data be read.
Table 9-1. Status Register Format – Byte 1
Note: 1. R = Readable only
Bit Name Type (1) Description
7 RDY/BUSY Ready/Busy Status R
0 Device is busy with an internal operation.
1 Device is ready.
6 COMP Compare Result R
0 Main memory page data matches buffer data.
1 Main memory page data does not match buffer data.
5:2 DENSITY Density Code R 0111 4-Mbit
1 PROTECT Sector Protection Status R
0 Sector protection is disabled.
1 Sector protection is enabled.
0 PAGE SIZE Page Size Configuration R
0 Device is configured for standard DataFlash page size (264 bytes).
1 Device is configured for “power of 2” binary page size (256 bytes).