Rainbow Electronics AT45DQ321 - Manual (Page 42)

42 AT45DQ321 [ADVANCE DATASHEET]
DS-45DQ321-031–DFLASH–12/2012
11. Buffer and Page Size Configuration
The memory array of DataFlash devices is actually larger than other Serial Flash devices in that extra user-accessible
bytes are provided in each page of the memory array. For the AT45DQ321, there are an extra 16 bytes of memory in
each page for a total of an extra 128KB (1-Mbits) of user-accessible memory. Therefore, the device density is actually
33-Mbits instead of 32-Mbits.
Some applications, however, may not want to take advantage of this extra memory and instead architect their software to
operate on a “power of 2” binary, logical addressing scheme. To allow this, the DataFlash can be configured so that the
buffer and page sizes are 512 bytes instead of the standard 528 bytes. In addition, the configuration of the buffer and
page sizes is reversible and can be changed from 528 bytes to 512 bytes or from 512 bytes to 528 bytes. The configured
setting is stored in an internal nonvolatile register so that the buffer and page size configuration is not affected by power
cycles. The nonvolatile register has a limit of 10,000 erase/program cycles; therefore, care should be taken to not switch
between the size options more than 10,000 times.
Devices are initially shipped from Adesto with the buffer and page sizes set to 528 bytes. Devices can be ordered from
Adesto pre-configured for the “power of 2” binary size of 512 bytes. For details, see
Section 27., Ordering Information on
page 74 .
To configure the device for “power of 2” binary page size (512 bytes), a 4-byte opcode sequence of 3Dh, 2Ah, 80h, and
A6h must be clocked into the device. After the last bit of the opcode sequence has been clocked in, the CS pin must be
deasserted to initiate the internally self-timed configuration process and nonvolatile register program cycle. The
programming of the nonvolatile register should take place in a time of t
EP
, during which time the RDY/BUSY bit in the
Status Register will indicate that the device is busy. The device does not need to be power cycled after the completion of
the configuration process and register program cycle in order for the buffer and page size to be configured to 512 bytes.
To configure the device for standard DataFlash page size (528 bytes), a 4-byte opcode sequence of 3Dh, 2Ah, 80h, and
A7h must be clocked into the device. After the last bit of the opcode sequence has been clocked in, the CS pin must be
deasserted to initial the internally self-timed configuration process and nonvolatile register program cycle. The
programming of the nonvolatile register should take place in a time of t
EP
, during which time the RDY/BUSY bit in the
Status Register will indicate that the device is busy. The device does not need to be power cycled after the completion of
the configuration process and register program cycle in order for the buffer and page size to be configured to 528 bytes.
Table 11-1. Buffer and Page Size Configuration Commands
Figure 11-1. Buffer and Page Size Configuration
Command Byte 1 Byte 2 Byte 3 Byte 4
“Power of 2” binary page size (512 bytes) 3Dh 2Ah 80h A6h
DataFlash page size (528 bytes) 3Dh 2Ah 80h A7h
CS
SI 3Dh 2Ah 80h
Opcode
Byte 4
Each transition represents eight bits