word address and data word byte indicates the Security register is not currently locked. A NACK response indicates

the AT24CSW01x/AT24CS02x is already locked. Please refer to Determining the Lock State of the Security Register

for details about determining the Lock status of the AT24CSW01x/AT24CS02x.

The sequence completes with a Stop condition being sent to the device, which initiates a self-timed internal write

cycle. The Lock operation will conclude upon completion of that write cycle, subsequently making the Security

register permanently read-only. Read operations are always allowed to the device.

Figure 10-3. Lock Command

SCL

SDA

Device Address Byte

Word Address Byte

Data Word (”Don’t Care” bits)

Start

by

Host

ACK

from

Client

MSb

MSb

Stop

by

Host

MSb

1

2

3

4

5

6

7

8

9

1

0

1

1

#

#

#

0

0

1

2

3

4

5

6

7

8

9

X

X

X

X

X

X

X

X

0

0

1

1

0

X

X

X

X

0

1

2

3

4

5

6

7

8

9

ACK

from

Client

ACK

from

Client

Note:  # indicates the hardware address value which is managed by the ordering code of the device (see Table 6-2).

10.3.2

Determining the Lock State of the Security Register

The Lock state of the device can be determined by sending a subset of the Lock command to the device. Only the

device address byte and word address byte need to be transmitted to the device to determine the Lock state. An ACK

response to the word address byte indicates the Lock has not been set while a NACK response indicates the Lock

has been set. If the Lock has already been set, it cannot be undone. The abbreviated Lock sequence is completed by

the host sending a Stop condition to the device.

Figure 10-4. Determining the Security Register Lock State

SCL

SDA

Device Address Byte

Word Address Byte

Start

by

Host

ACK

from

Client

MSb

MSb

Stop

by

Host

1

2

3

4

5

6

7

8

9

1

0

1

1

#

#

#

0

0

1

2

3

4

5

6

7

8

9

0

1

1

0

X

X

X

X 0/1

ACK from Client

if Unlocked

NACK from Client

if Locked

Note:  # indicates the hardware address value which is managed by the ordering code of the device (see Table 6-2).

AT24CSW01X/AT24CSW02X

Security Register

and its subsidiaries

Datasheet

DS20006396B-page 29