M28W320 STMicroelectronics, M28W320 Datasheet - Page 14

• Manufacturer Part Number: M28W320
• Description: 32 Mbit 2Mb x16/ Boot Block Low Voltage Flash Memory
• Manufacturer: STMicroelectronics

M28W320CT, M28W320CB
BLOCK PROTECTION
The M28W320C provide a flexible protection of all
the memory providing the protection unprotection
and locking of any blocks. All blocks are protected
at power-up. Each block of the array has two lev-
els of protection against program or erase opera-
tion. The first level is set by the Block Protect
instruction; a protected block cannot be pro-
grammed or erased until a Block Unprotect in-
struction is given for that block. A second level of
protection is set by the Block Lock instruction, and
requires the use of the WP pin, according to the
following scheme:
– when WP is at V
– when WP is at V
– the lock status is cleared for all blocks at power
The protection and lock status can be monitored
for each block using the Read Electronic Signature
(RSIG) instruction. Protected blocks will output a
’1’ on DQ0 and locked blocks will output a ’1’ in
DQ1.
Figure 4. Security Block Memory Map
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and all blocks can be protected or unprotected;
locked blocks are protected, regardless of their
previous protect state, and protection status
cannot be changed. Blocks that are not locked
can still change their protection status;
up.
Parameter Block # 0
IH
IL
, the Lock status is overridden
, Lock status is enabled; the
88h
85h
84h
81h
80h
Protection Register Lock
PROTECTION REGISTER
and SECURITY BLOCK
The M28W320C features a 128-bit protection reg-
ister and a security Block in order to increase the
protection of a system design. The Protection
Register is divided in two 64-bit segment. The first
segment (81h to 84h) is a unique device number,
while the second one (85h to 88h) can be pro-
grammed by the user. When shipped the user pro-
grammable segment is read at ’1’. It can be only
programmed at ’0’;
The user programmable segment can be protect-
ed writing the bit 1 of the Protection Lock register
(80h). The bit 1 protect also the bit 2 of the Protec-
tion Lock Register. The M28W320C feature a se-
curity Block. The security Block is located at
1FF000-1FFFFF (M28W320CT) or at 000000-
000FFF (M28W320CB) of the device. This block
can be permanently protected by the user pro-
gramming the bit 2 of the Protection Lock Register.
The protection Register and the Protection Lock
Register can be read using the RSIG command. A
subsequent read in the address starting from 80h
to 88h, the user will retrieve respectively the Pro-
tection Lock register, the unique device number
segment and the OTP user programmable register
segment (see Table 8).
User Programmable OTP
Unique device number
2
1
0
AI03523