Rainbow Electronics AT45DB021D - Manual (Page 10)

10
3638K–DFLASH–11/2012
AT45DB021D
5.8 Main Memory Page Program Through Buffer
This operation is a combination of the Buffer Write and Buffer to Main Memory Page Program with Built-in Erase
operations. Data is first clocked into the buffer from the input pin (SI) and then programmed into a specified page in
the main memory. To perform a main memory page program through buffer for the DataFlash standard page size
(264-bytes), a 1-byte opcode, 82H, must first be clocked into the device, followed by three address bytes. The
address bytes are comprised of five don’t care bits, 10 page address bits, (PA9 - PA0) that select the page in the
main memory where data is to be written, and nine buffer address bits (BFA8 - BFA0) that select the first byte in
the buffer to be written. To perform a main memory page program through buffer for the binary page size (256-
bytes), the opcode 82H must be clocked into the device followed by three address bytes consisting of six don’t care
bits, 10 page address bits (A17 - A8) that specify the page in the main memory to be written, and eight buffer
address bits (BFA7 - BFA0) that selects the first byte in the buffer to be written. After all address bytes are clocked
in, the part will take data from the input pins and store it in the specified data buffer. If the end of the buffer is
reached, the device will wrap around back to the beginning of the buffer. When there is a low-to-high transition on
the CS pin, the part will first erase the selected page in main memory to all ones and then program the data stored
in the buffer into that memory page. Both the erase and the programming of the page are internally self-timed and
should take place in a maximum time of t
EP
. During this time, the status register will indicate that the part is busy.
6. Sector Protection
Two protection methods, hardware and software controlled, are provided for protection against inadvertent or
erroneous program and erase cycles. The software controlled method relies on the use of software commands to
enable and disable sector protection while the hardware controlled method employs the use of the Write Protect
(WP) pin. The selection of which sectors that are to be protected or unprotected against program and erase
operations is specified in the nonvolatile Sector Protection Register. The status of whether or not sector protection
has been enabled or disabled by either the software or the hardware controlled methods can be determined by
checking the Status Register.
6.1 Software Sector Protection
6.1.1 Enable Sector Protection Command
Sectors specified for protection in the Sector Protection Register can be protected from program and erase
operations by issuing the Enable Sector Protection command. To enable the sector protection using the software
controlled method, the CS pin must first be asserted as it would be with any other command. Once the CS pin has
been asserted, the appropriate 4-byte command sequence must be clocked in via the input pin (SI). After the last
bit of the command sequence has been clocked in, the CS pin must be deasserted after which the sector
protection will be enabled.
Table 6-1. Enable Sector Protection Command
Figure 6-1. Enable Sector Protection
Command Byte 1 Byte 2 Byte 3 Byte 4
Enable Sector Protection 3DH 2AH 7FH A9H
Opcode
Byte 1
Opcode
Byte 2
Opcode
Byte 3
Opcode
Byte 4
CS
Each transition
represents 8 bits
SI