11

0291S–FLASH–11/08

AT29C020

18. Software Data Protection

Enable Algorithm

(1)

LOAD DATA AA

TO

ADDRESS 5555

LOAD DATA 55

TO

ADDRESS 2AAA

LOAD DATA A0

TO

ADDRESS 5555

LOAD DATA

TO

WRITES ENABLED

ENTER DATA

19. 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 55

TO

ADDRESS 2AAA

LOAD DATA 20

TO

ADDRESS 5555

LOAD DATA

TO

EXIT DATA

20. Software Protected Program Cycle Waveform

(1)(2)(3)

Notes:

1. A8 through A17 must specify the sector address during each high-to-low transition of WE (or CE) after the software code has

been entered.

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

3. All bytes that are not loaded within the sector being programmed will be indeterminate.

Notes:

1. Data Format: I/O7 - I/O0 (Hex); Address Format: A14 - A0 (Hex).

2. Data Protect state will be activated at end of program cycle.

3. Data Protect state will be deactivated at end of program period.

4. 256 bytes of data MUST BE loaded.