Rainbow Electronics AT45DB021B - Manual (Page 7)

7
AT45DB021B
1937F–DFLSH–10/02
MAIN MEMORY PAGE PROGRAM THROUGH BUFFER: This operation is a combina-
tion of the Buffer Write and Buffer to Main Memory Page Program with Built-in Erase
operations. Data is first shifted into buffer 1 or buffer 2 from the SI pin and then pro-
grammed into a specified page in the main memory. To initiate the operation, an 8-bit
opcode (82H for buffer 1 or 85H for buffer 2) must be followed by the five reserved bits
and 20 address bits. The 10 most-significant address bits (PA9 -PA0) select the page in
the main memory where data is to be written, and the next nine address bits (BFA8 -
BFA0) select the first byte in the buffer to be written. After all address bits are shifted in,
the part will take data from the SI pin and store it in one of the data buffers. 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 1s and then program the data stored in the buffer into the
specified page in the main memory. Both the erase and the programming of the page
are internally self-timed and should take place in a maximum of time t
EP
. During this
time, the status register will indicate that the part is busy.
Additional Commands MAIN MEMORY PAGE TO BUFFER TRANSFER: A page of data can be transferred
from the main memory to either buffer 1 or buffer 2. To start the operation, an 8-bit
opcode, 53H for buffer 1 and 55H for buffer 2, must be followed by the five reserved bits,
10 address bits (PA9-PA0) which specify the page in main memory that is to be trans-
ferred, and nine don’t care bits. The CS pin must be low while toggling the SCK pin to
load the opcode, the address bits, and the don’t care bits from the SI pin. The transfer of
the page of data from the main memory to the buffer will begin when the CS pin transi-
tions from a low to a high state. During the transfer of a page of data (t
XFR
), the status
register can be read to determine whether the transfer has been completed or not.
MAIN MEMORY PAGE TO BUFFER COMPARE: A page of data in main memory can
be compared to the data in buffer 1 or buffer 2. To initiate the operation, an 8-bit opcode
(60H for buffer 1 and 61H for buffer 2) must be followed by 24 address bits consisting of
the five reserved bits, 10 address bits (PA9 -PA0) which specify the page in the main
memory that is to be compared to the buffer, and nine don’t care bits. The CS pin must
be low while toggling the SCK pin to load the opcode, the address bits and the don’t
care bits from the SI pin. On the low-to-high transition of the CS pin, the 264 bytes in the
selected main memory page will be compared with the 264 bytes in buffer 1 or buffer 2.
During this time (t
XFR
), the status register will indicate that the part is busy. On comple-
tion of the compare operation, bit 6 of the status register is updated with the result of the
compare.
AUTO PAGE REWRITE: This mode is needed only if multiple bytes within a page or
multiple pages of data are modified in a random fashion. This mode is a combination of
two operations: Main Memory Page to Buffer Transfer and Buffer to Main Memory Page
Program with Built-in Erase. A page of data is first transferred from the main memory to
buffer 1 or buffer 2, and then the same data (from buffer 1 or buffer 2) is programmed
back into its original page of main memory. To start the rewrite operation, an 8-bit
opcode (58H for buffer 1 or 59H for buffer 2) must be followed by the five reserved bits,
10 address bits (PA9 -PA0) that specify the page in main memory to be rewritten, and
nine additional don’t care bits. When a low-to-high transition occurs on the CS pin, the
part will first transfer data from the page in main memory to a buffer and then program
the data from the buffer back into same page of main memory. The operation is inter-
nally 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.