Device operation – Rainbow Electronics AT45DB021E User Manual
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AT45DB021E [PRELIMINARY DATASHEET]
8789B–DFLASH–11/2012
4.
Device Operation
The device operation is controlled by instructions from the host processor. The list of instructions and their associated
opcodes are contained in
. A valid instruction starts with the falling
edge of CS followed by the appropriate 8-bit opcode and the Buffer or main memory address location. While the CS pin
is low, toggling the SCK pin controls the loading of the opcode and the Buffer or main memory address location through
the SI (Serial Input) pin. All instructions, addresses, and data are transferred with the Most Significant Bit (MSB) first.
Three address bytes are used to address memory locations in either the main memory array or in the Buffer. The three
address bytes will be comprised of a number of dummy bits and a number of actual device address bits, with the number
of dummy bits varying depending on the operation being performed and the selected device page size. Buffer addressing
for the standard DataFlash page size (264 bytes) is referenced in the datasheet using the terminology BFA8 - BFA0 to
denote the nine address bits required to designate a byte address within the Buffer. The main memory addressing is
referenced using the terminology PA9 - PA0 and BA8 - BA0, where PA9 - PA0 denotes the 10 address bits required to
designate a page address, and BA8 - BA0 denotes the nine address bits required to designate a byte address within the
page. Therefore, when using the standard DataFlash page size, a total of 22 address bits are used.
For the “power of 2” binary page size (256 bytes), the Buffer addressing is referenced in the datasheet using the
conventional terminology BFA7 - BFA0 to denote the eight address bits required to designate a byte address within the
Buffer. Main memory addressing is referenced using the terminology A17 - A0, where A17 - A8 denotes the 10 address
bits required to designate a page address, and A7 - A0 denotes the eight address bits required to designate a byte
address within a page. Therefore, when using the binary page size, a total of 21 address bits are used.