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

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’tcare 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-

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’tcare 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.

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-

status register will indicate that the part is busy.