10
0007N–PEEPR–9/09
AT28HC256
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
ANY ADDRESS
(4)
LOAD LAST BYTE
TO
LAST ADDRESS
ENTER DATA
PROTECT STATE
WRITES ENABLED
(2)
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
ANY ADDRESS
(4)
LOAD LAST BYTE
TO
LAST ADDRESS
LOAD DATA 55
TO
ADDRESS 2AAA
EXIT DATA
PROTECT STATE
(3)
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.
