AT25DF641A datasheet(13/57 Pages) ATMEL

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8693A–DFLASH–8/10

Atmel AT25DF641A [Preliminary]

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 com-

mand, 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 20) 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 opcode of A2h must be clocked into the device followed by

the three address bytes denoting the first byte location of the memory array to begin program-

ming 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 SOI and SI pins.

The data is always input with the MSB of a byte first, and the MSB is always input on the SOI

pin. During the first clock cycle, bit seven of the first data byte would be input on the SOI pin

while bit 6 of the same data byte would be input on the SI pin. During the next clock cycle, bits

five and four of the first data byte would be input on the SOI and SI pins, respectively. The

sequence would continue 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 is stored in an inter-

nal 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 to

be programmed will apply. In this situation, any data that is sent to the device that goes beyond

the end of the page will wrap around back to the beginning of the same page. 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 will be programmed at addresses 0000FEh and 0000FFh while

the last byte of data will be programmed at address 000000h. The remaining bytes in the page

(addresses 000001h through 0000FDh) will not be programmed and will remain in the erased

state (FFh). In addition, if more than 256-bytes of data are sent to the device, then only the last

256-bytes sent will be latched into the internal buffer.

When the CS pin is deasserted, the device will take the data stored in the internal buffer and pro-

gram it into the appropriate memory array locations based on the starting address specified by

A23-A0 and the number of data bytes sent to the device. If less than 256-bytes of data were sent

to the device, then the remaining bytes within the page will not be programmed and will remain

in the erased state (FFh). The programming of the data bytes is internally self-timed and should

take place in a time of t

PP or tBP if only programming a single byte.

The three address bytes and at least one complete byte of data must be clocked into the device

before the CS pin is deasserted, and the CS pin must be deasserted on even byte boundaries

(multiples of eight bits); otherwise, the device will abort the operation and no data will be pro-

grammed into the memory array. In addition, if the address specified by A23-A0 points to a

memory location within a sector that is in the protected state (see “Protect Sector” on page 21)

or locked down (see “Sector Lockdown” on page 28), then the Byte/Page Program command will

not be executed, and the device will return to the idle state once the CS pin has been deas-

serted. The WEL bit in the Status Register will be reset back to the logical “0” state if the

program cycle aborts due to an incomplete address being sent, an incomplete byte of data being

sent, the CS pin being deasserted on uneven byte boundaries, or because the memory location

to be programmed is protected or locked down.

AT25DF641A Datasheet(PDF) 13 Page - ATMEL Corporation

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