User guide

10
AT29C020
0291N–FLASH–07/02
Software Data Protection Enable Algorithm
()
LOAD DATA AA
TO
ADDRESS 5555
LOAD DATA 55
TO
ADDRESS 2AAA
LOAD DATA A0
TO
ADDRESS 5555
LOAD DATA
TO
PAGE (128 BYTES)
(4)
WRITES ENABLED
ENTER DATA
PROTECT STATE
(2)
Software Data Protection Disable Algorithm
()
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
PAGE (128 BYTES)
(4)
EXIT DATA
PROTECT STATE
(3)
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.
Software Protected Program Cycle Waveform
(1)(4)(5)
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.
4. OE
must be high when WE and CE are both low.
5. All bytes that are not loaded within the sector being programmed will be indeterminate.