AT25DF321A-MH-Y datasheet(14/58 Pages) ATMEL

14 / 58 page

3686C–DFLASH–12/08

AT25DF321A [Preliminary]

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 22)

or locked down (see “Sector Lockdown” on page 29), 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.

While the device is programming, the Status Register can be read and will indicate that the

device is busy. For faster throughput, it is recommended that the Status Register be polled

rather than waiting the t

BP or tPP time to determine if the data bytes have finished programming.

At some point before the program cycle completes, the WEL bit in the Status Register will be

reset back to the logical “0” state.

The device also incorporates an intelligent programming algorithm that can detect when a byte

location fails to program properly. If a programming error arises, it will be indicated by the EPE

bit in the Status Register.

Figure 8-3.

Dual-Input Byte Program

SCK

SOI

MSB

10100010

410 11

812

31 32

29 30

OPCODE

AAAA

AAA

ADDRESS BITS A23-A0

MSB

INPUT

DATA BYTE

HIGH-IMPEDANCE

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