Software Data Protection
Enable Algorithm(1)
Software Data Protection
Disable Algorithm(1)
LOAD DATA AA
TO
LOAD DATA AA
TO
ADDRESS 5555
ADDRESS 5555
LOAD DATA 55
TO
LOAD DATA 55
TO
ADDRESS 2AAA
ADDRESS 2AAA
LOAD DATA A0
TO
LOAD DATA 80
TO
ADDRESS 5555
WRITES ENABLED(2)
ADDRESS 5555
LOAD DATA
TO
PAGE (64 BYTES)(4)
LOAD DATA AA
TO
ENTER DATA
PROTECT STATE
ADDRESS 5555
Notes: 1. Data Format: I/O7 - I/O0 (Hex);
Address Format: A14 - A0 (Hex).
2. Data Protect state will be re-activated at end of pro-
gram cycle.
LOAD DATA 55
TO
ADDRESS 2AAA
3. Data Protect state will be deactivated at end of pro-
gram period.
4. 64 bytes of data MUST BE loaded.
LOAD DATA 20
TO
ADDRESS 5555
EXIT DATA
PROTECT STATE(3)
LOAD DATA
TO
PAGE (64 BYTES)(4)
Software Protected Program Cycle Waveform(1)(2)(3)
Notes: 1. A6 through A14 must specify the page 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 page being programmed will be indeterminate.
10
AT29C256
0046P–FLASH–10/04
ATMEL [ ATMEL ]
