Device operation – Rainbow Electronics AT45DB041E User Manual
Page 6
6
AT45DB041E [ADVANCE DATASHEET]
8783B–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 (264 bytes) is referenced in the datasheet using the
terminology BFA8 - BFA0 to denote the 9 address bits required to designate a byte address within a buffer. The main
memory addressing is referenced using the terminology PA10 - PA0 and BA8 - BA0, where PA10 - PA0 denotes the
11 address bits required to designate a page address, and BA8 - BA0 denotes the 9 address bits required to designate a
byte address within the page. Therefore, when using the standard DataFlash page size, a total of 20 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 a
buffer. Main memory addressing is referenced using the terminology A18 - A0, where A18 - A8 denotes the 11 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 19 address bits are used.