MBM29PL12LM Fujitsu Media Devices, MBM29PL12LM Datasheet - Page 33

• Manufacturer Part Number: MBM29PL12LM
• Description: FLASH MEMORY 128 M (16M x 8/8M x 16) BIT
• Manufacturer: Fujitsu Media Devices

HiddenROM Mode
The HiddenROM (HiddenROM) feature provides a Flash memory region that the system may access through
a new command sequence. This is primarily intended for customers who wish to use an Electronic Serial Number
(ESN) in the device with the ESN protected against modification. Once the HiddenROM region is protected, any
further modification of that region is impossible. This ensures the security of the ESN once the product is shipped
to the field.
The HiddenROM region is 256 bytes / 128 words in length. After the system writes the HiddenROM Entry
command sequence, it may read the HiddenROM region by using device addresses A
“0”). That is, the device sends only program command that would normally be sent to the address to the
HiddenROM region. This mode of operation continues until the system issues the Exit HiddenROM command
sequence, or until power is removed from the device. On power-up, or following a hardware reset, the device
reverts to sending commands to the address.
If you request Fujitsu to program the ESN in the device, please contact a Fujitsu representative for more
information.
The device has a HiddenROM region with One Time Protect function. This area is to enter the security code
and to unable the change of the code once set. Programming is allowed in this area until it is protected. However,
once it gets protected, it is impossible to unprotect. Therefore, extreme caution is required.
The HiddenROM region is 256 bytes / 128 words. This area is in SA0 . Therefore, write the HiddenROM entry
command sequence to enter the HiddenROM region. It is called HiddenROM mode when the HiddenROM region
appears.
Sectors other than the block area SA0 can be read during HiddenROM mode. Read/program of the HiddenROM
region is possible during HiddenROM mode. Write the HiddenROM reset command sequence to exit the Hid-
denROM mode. Note that any other commands should not be issued than the HiddenROM program/protection/
reset commands during the HiddenROM mode. When you issue the other commands including the suspend
resume capability, send the HiddenROM reset command first to exit the HiddenROM mode and then issue each
command.
To program the data to the HiddenROM region, write the HiddenROM program command sequence during
HiddenROM mode. This command is the same as the usual program command, except that it needs to write
the command during HiddenROM mode. Therefore the detection of completion method is the same as in the
past, using the DQ
programmed. If an address not in the HiddenROM region is selected, the previous data will be deleted.
During the write into the HiddenROM region, the program suspend command issuance is prohibited.
There are two methods to protect the HiddenROM region. One is to write the sector group protect setup command
(60h) , set the sector address in the HiddenROM region and (A
sector group protect command (60h) during the HiddenROM mode. The same command sequence may be used
because it is the same as the extension sector group protect in the past, except that it is in the HiddenROM
mode and does not apply high voltage to the RESET pin. Please refer to above mentioned “Extended Sector
Group Protection” for details of sector group protect setting.
The other method is to apply high voltage (V
and (A
protect circuit, apply high voltage (V
in the HiddenROM region, and read. When “1” appears on DQ
on DQ
method because other than the HiddenROM mode, it is the same as the sector group protect previously men-
tioned.
(1) HiddenROM Region
(2) HiddenROM Entry Command
(3) HiddenROM Program Command
(4) HiddenROM Protect Command
0
6
, A
if it is not protected. Apply write pulse again. The same command sequence could be used for the above
3
, A
2
, A
1
, A
7
0
data pooling, DQ
) = (0, 0, 0, 1, 0) , and apply the write pulse during the HiddenROM mode. To verify the
ID
) to A
6
Toggle bit or RY/BY. You should pay attention to the address to be
9
, specify (A
ID
) to A
9
and OE, set the sector address in the HiddenROM region
6
, A
3
, A
0
2
, the protect setting is completed. “0” will appear
, A
6
, A
1
, A
3
, A
0
) = (0, 0, 0, 1, 0) and the sector address
2
, A
MBM29PL12LM
1
, A
0
) = (0, 0, 0, 1, 0) , and write the
6
to A
0
(A
22
to A
15
are all
10
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