AT25320B_14 Datasheet, PDF (10/24 Pages) ATMEL Corporation – SPI Serial EEPROM

Write Sequence (Write): In order to program the AT25320B/640B, two separate instructions must be executed. First,
the device must be write enabled via the WREN instruction. Then a 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 opcode
is transmitted via the SI line followed by the byte address (A15–A0) and the data (D7–D0) to be programmed (see Table
5-6). 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 rollover 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 5-6. Address Key
Address
A_N
Don’t Care Bits
AT25320B
A₁₁–A₀
A₁₅–A₁₂
AT25640B
A₁₂–A₀
A₁₅–A₁₃
Atmel AT25320B/640B [DATASHEET] 10
8535G–SEEPROM–11/2012