CAT24M01

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6

WRITE OPERATIONS

Byte Write

In Byte Write mode the Master sends a START, followed

by Slave address, two byte address and data to be written

(Figure 6). The Slave acknowledges all 4 bytes, and the

Master then follows up with a STOP, which in turn starts the

internal Write operation (Figure 7). During internal Write,

the Slave will not acknowledge any Read or Write request

from the Master.

Page Write

The CAT24M01 contains 131,072 bytes of data, arranged

in 512 pages of 256 bytes each. The most significant 9 bits

of the address word (a16 from the Slave Address byte and

most significant Address byte) identify the page and the last

8 bits identify the byte within the page. The 17−bit address

word (a16 from the Slave Address byte followed by two

address bytes) points to the first byte to be written. Up to 256

bytes can be written in one Write cycle (Figure 8).

The internal byte address counter is automatically

incremented after each data byte is loaded. If the Master

transmits more than 256 data bytes, then earlier bytes will be

overwritten by later bytes in a ‘wrap−around’ fashion

(within the selected page). The internal Write cycle starts

immediately following the STOP.

During an internal Write operation, new data provided

by Byte Write or Page Write instructions will replace data

previously stored at the corresponding address locations,

while data stored at all other address locations within the

same page will be refreshed. Thus, whether writing one

byte or 256 bytes to a page, the entire page will be

reprogrammed with the corresponding combination of

new and old data.

Acknowledge Polling

Acknowledge polling can be used to determine if the

CAT24M01 is busy writing or is ready to accept commands.

Polling is implemented by interrogating the device with a

‘Selective Read’ command (see READ OPERATIONS).

The CAT24M01 will not acknowledge the Slave address,

as long as internal Write is in progress.

Hardware Write Protection

With the WP pin held HIGH, the entire memory is

protected against Write operations. If the WP pin is left

floating or is grounded, it has no impact on the operation of

the CAT24M01. The state of the WP pin is strobed on the last

falling edge of SCL immediately preceding the first data

byte (Figure 9). If the WP pin is HIGH during the strobe

interval, the CAT24M01 will not acknowledge the data byte

and the Write request will be rejected.

Delivery State

The CAT24M01 is shipped erased, i.e., all bytes are FFh.