AT25640B(2010) データシートの表示（PDF） - Atmel Corporation

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AT25640B
(Rev.:2010)

SPI Serial EEPROMs 32K (4096 x 8) 64K (8192 x 8)

Atmel Corporation 

Atmel AT25320B/640B

WRITE SEQUENCE (WRITE): In order to program the Atmel® AT25320B/640B, two separate instructions must be

executed. First, the device must be write enabled via the WREN instruction. Then a write (WRITE) instruction

may be executed. Also, the address of the memory location(s) to be programmed must be outside the protected

address field location selected by the block write protection level. During an internal write cycle, all commands will

be ignored except the RDSR instruction.

A write instruction requires the following sequence. After the CS line is pulled low to select the device, the WRITE

op-code is transmitted via the SI line followed by the byte address (A15–A0) and the data (D7–D0) to be pro-

grammed (see Table 3-6). Programming will start after the CS pin is brought high. The low-to-high transition of the

CS pin must occur during the SCK low-time immediately after clocking in the D0 (LSB) data bit.

The READY/BUSY status of the device can be determined by initiating a read status register

(RDSR) instruction. If Bit 0 = “1”, the write cycle is still in progress. If Bit 0 = “0”, the write cycle has ended. Only the

RDSR instruction is enabled during the write programming cycle.

The AT25320B/640B is capable of a 32-byte page write operation. After each byte of data is received, the five low-

order address bits are internally incremented by one; the high-order bits of the address will remain constant. If

more than 32-bytes of data are transmitted, the address counter will roll over and the previously written data will be

overwritten. The AT25320B/640B is automatically returned to the write disable state at the completion of a write

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 reinitiate the serial communication.

Table 3-6. Address Key

Address

AN

Don’t Care Bits

Atmel AT25320B

A11–A0

A15–A12

Atmel AT25640B

A12–A0

A15–A13

9

8535F–SEEPR–6/10

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