11

AT25FS040

5107D–SFLSH–09/06

progress. If Bit 0=0, the programming cycle has ended. Only the RDSR instruction is

enabled during the programming cycle and all other opcode instructions are ignored

until programming cycle has completed.

A single PROGRAM instruction programs 1 to 256 consecutive bytes within a page if it

is not write protected. The starting byte address can be anywhere within the page.

When the end of the page is reached, the address will wrap around to the beginning of

the same page. If the data to be programmed is less than a full page, the data of all

other bytes on the same page will remain unchanged meaning that the unwritten

address locations within the page will not be changed. If more than 256 bytes of data

are provided, the address counter will roll over on the same page and the previous data

provided will be replaced. The same byte cannot be reprogrammed without erasing the

whole sector or block first. The AT25FS040 will automatically return to the write disable

state at the completion of the programming cycle.

Note:

If the device is not write enabled (WREN), the device will ignore the Write instruction and

will return to the standby state when CS is brought high. A new CS falling edge is

required to re-initiate the serial communication.

ERASE OPERATION: The AT25FS040 memory array is internally organized into uni-

form 4K byte sectors or uniform 64K byte uniform blocks (see Table 12). Before data can

be reprogrammed, the sector or block that contains the data must be erased first. In

order to erase the AT25FS040, there are three flexible erase instructions that can be

executed as follows: SECTOR ERASE, BLOCK ERASE and CHIP ERASE instructions.

A SECTOR ERASE instruction allows erasing any individual 4K sector without changing

data in rest of memory. The BLOCK ERASE instruction allows erasing any individual

block and CHIP ERASE allows erasing the entire memory array.

SECTOR ERASE (SECTOR ERASE): The SECTOR ERASE instruction sets all 4K

bytes in the selected sector to logic 1 or erased state. In order to sector erase the

AT25FS040, two separate instructions must be executed. First, the device must be write

enabled via the WREN instruction. Then the SECTOR ERASE instruction can be exe-

cuted and will erase every byte in the selected sector if the sector is not locked out. The

sector address is automatically determined if any address within the sector is selected

(see Figure 12). The SECTOR ERASE instruction is internally controlled and self timed

to completion. During this time, all commands will be ignored except RDSR instruction.

The progress or completion of the erase operation can be determined by reading

ready/busy bit (bit 0) through RDSR instruction. If Bit 0=1, sector erase cycle is in

progress. If Bit 0=0, the erase operation has been completed. The AT25FS040 will auto-

Table 11. Address Key

Address

AT25FS040

Don’t Care Bits

A