AT25DF021A-DWFHT datasheet(17/59 Pages) RENESAS

17 / 59 page

DS-AT25DF021A-042 Rev. L

Page 17

8/7/23

AT25DF021A Datasheet

Figure 11. Byte Program

Figure 12. Page Program

8.2

Dual-Input Byte/Page Program

The Dual-Input Byte/Page Program command is similar to the standard Byte/Page Program command and can be

used to program anywhere from a single byte of data up to 256 bytes of data into previously erased memory

locations. Unlike the standard Byte/Page Program command, however, the Dual-Input Byte/Page Program

command allows two bits of data to be clocked into the device on every clock cycle rather than just one.

Before the Dual-Input Byte/Page Program command can be started, the Write Enable command must have been

previously issued to the device (see “Write Enable” on page 23) to set the Write Enable Latch (WEL) bit of the

Status Register to a Logical 1 state. To perform a Dual-Input Byte/Page Program command, an A2h opcode must

be clocked into the device followed by the three address bytes denoting the first location of the memory array to

begin programming at. After the address bytes have been clocked in, data can then be clocked into the device two

bits at a time on both the SO and SI pins.

The data is always input with the MSB of a byte first, and the MSB is always input on the SO pin. During the first

clock cycle, bit seven of the first data byte is input on the SO pin while bit six of the same data byte is input on the

SI pin. During the next clock cycle, bits five and four of the first data byte are input on the SO and SI pins,

respectively. The sequence continues with each byte of data being input after every four clock cycles. Like the

standard Byte/Page Program command, all data clocked into the device are stored in an internal buffer.

If the starting memory address denoted by A23-A0 does not fall on an even 256-byte page boundary (A7-A0 are

not all 0), then special circumstances regarding which memory locations are to be programmed apply. In this

situation, any data that are sent to the device that go beyond the end of the page wrap around to the beginning of

the same page. Also, if more than 256 bytes of data is sent to the device, then only the last 256 bytes sent are

latched into the internal buffer.

For example: If the starting address denoted by A23-A0 is 0000FEh and three bytes of data are sent to the device,

then the first two bytes of data are programmed at addresses 0000FEh and 0000FFh, while the last byte of data is

SCK

MSB

00000010

410 11

812

37 38

31 32

29 30

OPCODE

High-Impedance

AAAA

AAA

MSB

DDDDDDDD

ADDRESS BITS A23-A0

DATA IN

SCK

MSB

00000010

839

37 38

31 32

29 30

OPCODE

High-Impedance

AAA

MSB

DDDDDDDD

ADDRESS BITS A23-A0

DATA IN BYTE 1

MSB

DDDDDDDD

DATA IN BYTE n

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