10

0006M–PEEPR–12/09

AT28C256

19. Software Data Protection

Enable Algorithm(1)

Notes:

1. Data Format: I/O7 - I/O0 (Hex);

Address Format: A14 - A0 (Hex).

2. Write Protect state will be activated at end of write

even if no other data is loaded.

3. Write Protect state will be deactivated at end of write

period even if no other data is loaded.

4. 1 to 64 bytes of data are loaded.

LOAD DATA AA

TO

ADDRESS 5555

LOAD DATA 55

TO

ADDRESS 2AAA

LOAD DATA A0

TO

ADDRESS 5555

LOAD DATA XX

TO

LOAD LAST BYTE

TO

LAST ADDRESS

ENTER DATA

PROTECT STATE

20. Software Data Protection

Disable Algorithm(1)

LOAD DATA AA

TO

ADDRESS 5555

LOAD DATA 55

TO

ADDRESS 2AAA

LOAD DATA 80

TO

ADDRESS 5555

LOAD DATA AA

TO

ADDRESS 5555

LOAD DATA 20

TO

ADDRESS 5555

LOAD DATA XX

TO

LOAD LAST BYTE

TO

LAST ADDRESS

LOAD DATA 55

TO

ADDRESS 2AAA

EXIT DATA

21. Software Protected Write Cycle Waveforms(1)(2)

Notes:

1. A6 through A14 must specify the same page address during each high to low transition of WE (or CE) after the software

code has been entered.

2. OE must be high only when WE and CE are both low.