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.

LOAD LAST BYTE

TO

LAST ADDRESS

LOAD DATA A0

TO

ADDRESS 5555

LOAD DATA 55

TO

ADDRESS 2AAA

LOAD DATA AA

TO

ADDRESS 5555

Notes for software program code:

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.

ENTER DATA

PROTECT STATE

WRITES ENABLED

(2)

Software Data

Protection Enable Algorithm

(1)

LOAD DATA XX

TO

ANY ADDRESS

(4)

LOAD LAST BYTE

TO

LAST ADDRESS

LOAD DATA 55

TO

ADDRESS 2AAA

LOAD DATA AA

TO

ADDRESS 5555

LOAD DATA 80

TO

ADDRESS 5555

LOAD DATA 55

TO

ADDRESS 2AAA

LOAD DATA AA

TO

ADDRESS 5555

LOAD DATA 20

TO

ADDRESS 5555

EXIT DATA

PROTECT STATE

(3)

Software Data

Protection Disable Algorithm

(1)

LOAD DATA XX

TO

ANY ADDRESS

(4)

2-224

AT28C256