AT25DF321A datasheet(10/51 Pages) RENESAS

10 / 51 page

3686I–DFLASH–02/2019

AT25DF321A

Figure 7-4.

Dual-Output Read Array

Program and Erase Commands

8.1

Byte/Page Program

The Byte/Page Program command allows anywhere from a single byte of data to 256-bytes of data to be programmed into

previously erased memory locations. An erased memory location is one that has all eight bits set to the logical “1” state (a byte

value of FFh). Before a Byte/Page Program command can be started, the Write Enable command must have been previously

issued to the device (see “Write Enable” on page 18) to set the Write Enable Latch (WEL) bit of the Status Register to a logical

“1” state.

To perform a Byte/Page Program command, an opcode of 02h must be clocked into the device followed by the three address

bytes denoting the first byte 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 and will be 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 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 program 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

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 programmed 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 19) or locked down (see “Sector

Lockdown” on page 25

), 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 deasserted. 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.

SCK

SIO

MSB

10 11

42 43

37 38

31 32

29 30

47 48

OPCODE

MSB

ADDRESS BITS A23-A0

DON'T CARE

OUTPUT

DATA BYTE 1

OUTPUT

DATA BYTE 2

HIGH-IMPEDANCE

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