CAT28C64B
Toactivatethesoftwaredataprotection,thedevicemust
besentthreewritecommandstospecificaddresseswith
specific data (Figure 9). This sequence of commands
(along with subsequent writes) must adhere to the page
writetimingspecifications(Figure11).Oncethisisdone,
all subsequent byte or page writes to the device must be
preceded by this same set of write commands. The data
protection mechanism is activated until a deactivate
sequence is issued regardless of power on/off transi-
tions. This gives the user added inadvertent write pro-
tection on power-up in addition to the hardware protec-
tion provided.
To allow the user the ability to program the device with
an E2PROM programmer (or for testing purposes) there
is a software command sequence for deactivating the
data protection. The six step algorithm (Figure 10) will
reset the internal protection circuitry, and the device will
return to standard operating mode (Figure 12 provides
reset timing). After the sixth byte of this reset sequence
has been issued, standard byte or page writing can
commence.
Figure 11. Software Data Protection Timing
t
WC
DATA
ADDRESS
AA
1555
55
0AAA
A0
1555
BYTE OR
PAGE
CE
WRITES
ENABLED
t
t
BLC
WP
WE
5094 FHD F13
Figure 12. Resetting Software Data Protection Timing
t
DATA
ADDRESS
AA
1555
55
0AAA
80
1555
AA
1555
55
0AAA
20
1555
WC
SDP
RESET
CE
DEVICE
UNPROTECTED
WE
5094 FHD F14
ORDERING INFORMATION
Prefix
Device #
Suffix
CAT
28C64B
N
I
-15
T
Product
Number
Temperature Range
Tape & Reel
T: 500/Reel
Blank = Commercial (0˚C to +70˚C)
I = Industrial (-40˚C to +85˚C)
A = Automotive (-40˚ to +105˚C)*
Package
Optional
Company
ID
Speed
12: 120ns
15: 150ns
P: PDIP
J: SOIC (JEDEC)
K: SOIC (EIAJ)
N: PLCC
T13: TSOP (8mmx13.4mm)
* -40˚C to +125˚C is available upon request
28C64B F15
Notes:
(1) The device used in the above example is a CAT28C64BNI-15T (PLCC, Industrial temperature, 150 ns Access Time, Tape & Reel).
Doc. No. 25006-0A 2/98 P-1
11
CATALYST [ CATALYST SEMICONDUCTOR ]
