8

1937J–DFLSH–9/05

AT45DB021B

5.3

Additional Commands

5.3.1

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 transferred, 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 transitions from a

low to a high state. During the transfer of a page of data (t

determine whether the transfer has been completed or not.

5.3.2

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

pare operation, bit 6 of the status register is updated with the result of the compare.

5.3.3

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 oper-

ation, 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 internally self-timed and should

take place in a maximum time of t

part is busy.

If a sector is programmed or reprogrammed sequentially page-by-page, then the programming

algorithm shown in Figure 15-1 on page 25 is recommended. Otherwise, if multiple bytes in a

page or several pages are programmed randomly in a sector, then the programming algorithm

shown in Figure 15-2 on page 26 is recommended. Each page within a sector must be

updated/rewritten at least once within every 10,000 cumulative page erase/program operations

in that sector.