20 Am49DL640BG March 8, 2002
PRELIMINARY
Figure 2. In-System Sector Protect/Unprotect Algorithms
Sector Protect:
Write 60h to sector
address with
A6 = 0, A1 = 1,
A0 = 0
Set up sector
address
Wait 150 µs
Verify Sector
Protect: Write 40h
to sector address
with A6 = 0,
A1 = 1, A0 = 0
Read from
sector address
with A6 = 0,
A1 = 1, A0 = 0
START
PLSCNT = 1
RESET# = V
ID
Wait 1 µs
First Write
Cycle = 60h?
Data = 01h?
Remove V
ID
from RESET#
Write reset
command
Sector Protect
complete
Yes
Yes
No
PLSCNT
= 25?
Yes
Device failed
Increment
PLSCNT
Temporary Sector
Unprotect Mode
No
Sector Unprotect:
Write 60h to sector
address with
A6 = 1, A1 = 1,
A0 = 0
Set up first sector
address
Wait 15 ms
Verify Sector
Unprotect: Write
40h to sector
address with
A6 = 1, A1 = 1,
A0 = 0
Read from
sector address
with A6 = 1,
A1 = 1, A0 = 0
START
PLSCNT = 1
RESET# = V
ID
Wait 1 µs
Data = 00h?
Last sector
verified?
Remove V
ID
from RESET#
Write reset
command
Sector Unprotect
complete
Yes
No
PLSCNT
= 1000?
Yes
Device failed
Increment
PLSCNT
Temporary Sector
Unprotect Mode
No
All sectors
protected?
Yes
Protect all sectors:
The indicated portion
of the sector protect
algorithm must be
performed for all
unprotected sectors
prior to issuing the
first sector
unprotect address
Set up
next sector
address
No
Yes
No
Yes
No
No
Yes
No
Sector Protect
Algorithm
Sector Unprotect
Algorithm
First Write
Cycle = 60h?
Protect another
sector?
Reset
PLSCNT = 1
