19. Software Data Protection
Enable Algorithm(1)
20. Software Data Protection
Disable Algorithm(1)
LOAD DATA AA
LOAD DATA AA
TO
TO
ADDRESS 5555
ADDRESS 5555
LOAD DATA 55
TO
LOAD DATA 55
TO
ADDRESS 2AAA
ADDRESS 2AAA
LOAD DATA 80
TO
LOAD DATA A0
TO
ADDRESS 5555
ADDRESS 5555
WRITES ENABLED(2)
LOAD DATA AA
TO
LOAD DATA XX
TO
ANY ADDRESS(4)
ADDRESS 5555
LOAD DATA 55
TO
LOAD LAST BYTE
TO
ADDRESS 2AAA
LAST ADDRESS
ENTER DATA
PROTECT STATE
LOAD DATA 20
TO
Notes: 1. Data Format: I/O7 - I/O0 (Hex);
Address Format: A14 - A0 (Hex).
ADDRESS 5555
EXIT DATA
PROTECT STATE(3)
2. Write Protect state will be activated at end of write
even if no other data is loaded.
LOAD DATA XX
TO
ANY ADDRESS(4)
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 LAST BYTE
TO
LAST ADDRESS
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.
10
AT28C256
0006M–PEEPR–12/09
ATMEL [ ATMEL ]
