Device operation – Rainbow Electronics AT45DB642 User Manual
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AT45DB321E [PRELIMINARY DATASHEET]
8784B–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 desired buffer or main memory address location. While the
CS pin is low, toggling the SCK pin controls the loading of the opcode and the desired 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 one of the SRAM
buffers. 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 (528 bytes) is referenced in the datasheet using the
terminology BFA9 - BFA0 to denote the 10 address bits required to designate a byte address within a buffer. The main
memory addressing is referenced using the terminology PA12 - PA0 and BA9 - BA0, where PA12 - PA0 denotes the
13 address bits required to designate a page address, and BA9 - BA0 denotes the 10 address bits required to designate
a byte address within the page. Therefore, when using the standard DataFlash page size, a total of 23 address bits are
used.
For the “power of 2” binary page size (512 bytes), the buffer addressing is referenced in the datasheet using the
conventional terminology BFA8 - BFA0 to denote the nine address bits required to designate a byte address within a
buffer. Main memory addressing is referenced using the terminology A21 - A0, where A21 - A9 denotes the 13 address
bits required to designate a page address, and A8 - A0 denotes the nine address bits required to designate a byte
address within a page. Therefore, when using the binary page size, a total of 22 address bits are used.