AT25P1024

8

Writes are only allowed to sections of the memory which

are not block-protected.

Note:

When the WPEN bit is hardware write protected, it can-

not be changed back to “0”, as long as the WP pin is held

low.

READ SEQUENCE (READ):

Reading the AT25P1024

via the SO (Serial Output) pin requires the following

sequence. After the CS line is pulled low to select a device,

the READ op-code is transmitted via the SI line followed by

the byte address to be read (Refer to Table 6). Upon com-

pletion, any data on the SI line will be ignored. The data

(D7-D0) at the specified address is then shifted out onto

the SO line. If only one byte is to be read, the CS line

should be driven high after the data comes out. The READ

sequence can be continued since the byte address is auto-

matically incremented and data will continue to be shifted

out. When the highest address is reached, the address

counter will roll over to the lowest address allowing the

entire memory to be read in one continuous READ cycle.

WRITE SEQUENCE (WRITE):

In order to program the

AT25P1024, two separate instructions must be executed.

First, the device must be write enabled via the Write

Enable (WREN) Instruction. Then a Write (WRITE) Instruc-

tion may be executed. Also, the address of the memory

location(s) to be programmed must be outside the pro-

tected address field location selected by the Block Write

Protection Level. During an internal write cycle, all com-

mands 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

op-code is transmitted via the SI line followed by the byte

address and the data (D7-D0) to be programmed (Refer to

Table 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) Instruc-

tion. If Bit 0 = 1, the WRITE cycle is still in progress. If Bit 0

= 0, the WRITE cycle has ended. Only the READ STATUS

REGISTER instruction is enabled during the WRITE pro-

gramming cycle.

The AT25P1024 is capable of a 128-byte PAGE WRITE

operation ONLY. Content of the page in the array will not

be guaranteed if less than 128 bytes of data is received

(byte operation is not supported). After each byte of data is

received, the seven low order address bits are internally

incremented by one; the high order bits of the address will

remain constant. If more than 128 bytes of data are trans-

mitted, the address counter will roll over and the previously

written data will be overwritten. The AT25P1024 is auto-

matically returned to the write disable state at the comple-

tion 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 re-initiate the serial communication.

Table 5. WPEN Operation

WPEN

WP

WEN

Protected

Blocks

Unprotected

Blocks

Status

Register

0

X

0

Protected

Protected

Protected

0

X

1

Protected

Writable

Writable

1

Low

0

Protected

Protected

Protected

1

Low

1

Protected

Writable

Protected

X

High

0

Protected

Protected

Protected

X

High

1

Protected

Writable

Writable

Table 6. Address Key

Address

AT25P1024

A

N

A

Don’t Care Bits

A