AT34C02B View Datasheet(PDF) - Atmel Corporation

Part Name

Description

Manufacturer

AT34C02B

Two-wire Serial EEPROM with Permanent and Reversible Software Write Protect

Atmel Corporation 

Write Protection

The software write protection, once enabled, write protects only the first-half of the array

(00H - 7FH) while the hardware write protection, via the WP pin, is used to protect the

entire array.

PERMANENT SOFTWARE WRITE PROTECTION: The software write protection is

enabled by sending a command, similar to a normal write command, to the device which

programs the permanent write protect register. This must be done with the WP pin low.

The write protect register is programmed by sending a write command with the device

address of 0110 instead of 1010 with the address and data bit being don’t cares (see

Figure 7 on page 10). Once the software write protection has been enabled, the device

will no longer acknowledge the 0110 control byte. The software write protection cannot

be reversed even if the device is powered down. The write cycle time must be observed.

REVERSIBLE SOFTWARE WRITE PROTECTION: The reversible software write pro-

tection is enabled by sending a command, similar to a normal write command, to the

device which programs the reversible write protect register. This must be done with the

WP pin low. The write protect register is programmed by sending a write command

01100010 with pins A2 and A1 tied to ground or don't connect and pin A0 connected to

VHV (see Figure 8). The reversible write protection can be reversed by sending a com-

mand 01100110 with pin A2 tied to ground or no connect, pin A1 tied to VCC and pin A0

tied to VHV (see Figure 9).

HARDWARE WRITE PROTECTION: The WP pin can be connected to VCC, GND, or

left floating. Connecting the WP pin to VCC will write protect the entire array, regardless

of whether or not the software write protection has been enabled. The software write

protection register cannot be programmed when the WP pin is connected to VCC. If the

WP pin is connected to GND or left floating, the write protection mode is determined by

the status of the software write protect register.

Figure 7. Setting Permanent Write Protect Register (PSWP)

SDA LINE

S

T

CONTROL

A

R

BYTE

T

0 1 1 0 A2 A1 A0 0

WORD

ADDRESS

S

DATA

T

O

P

A

A

A

C

C

C

K

K

K

= Don't Care

Figure 8. Setting Reversible Write Protect Register (RSWP)

SDA LINE

S

T

CONTROL

A

BYTE

R

T

WORD

ADDRESS

S

DATA

T

O

P

01100 010

A

A

A

C

C

C

K

K

K

= Don't Care

Figure 9. Clearing Reversible Write Protect Register (RSWP)

SDA LINE

S

T

CONTROL

A

R

BYTE

T

WORD

ADDRESS

S

DATA

T

O

P

01100 110

A

A

A

C

C

C

K

K

K

= Don't Care

10 AT34C02B

3417E–SEEPR–1/07

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