MBM29DL34TF Fujitsu Media Devices, MBM29DL34TF Datasheet - Page 32

• Manufacturer Part Number: MBM29DL34TF
• Description: (MBM29DL34BF/TF) FLASH MEMORY CMOS 32 M (4 M X 8/2 M X 16) BIT
• Manufacturer: Fujitsu Media Devices

32
MBM29DL34TF/BF
9. HiddenROM Region
10. HiddenROM Entry Command
11. HiddenROM Program Command
12. HiddenROM Protect Command
(4) Query Command (CFI : Common Flash Memory Interface)
The CFI (Common Flash Memory Interface) specification outlines device and host system software interrogation
handshake which allows specific vendor-specified software algorithms to be used for entire families of devices.
This allows device-independent, JEDEC ID-independent, and forward-and backward-compatible software sup-
port for the specified flash device families. Refer to Common Flash memory Interface code.
The operation is initiated by writing the query command (98h) into the command register. The bank address
should be set when writing this command. Then the device information can be read from the bank, and an actual
data of memory cell be read from the another bank. Following the command write, a read cycle from specific
address retrieves device information. Please note that output data of upper byte (DQ
mode (16 bit) read. Refer to the Common Flash memory Interface code table. To terminate operation, it is
necessary to write the Reset command sequence into the register. (See “Common Flash Memory Interface
Code Table” in
The 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 in length and is stored at the same address of the 8 KB sectors. The
MBM29DL34TF occupies the address of the byte mode 3FE000h to 3FE0FFh (word mode 1FF000h to 1FF07Fh)
and the MBM29DL34BF type occupies the address of the byte mode 000000h to 0000FFh (word mode 000000h
to 00007Fh) . After the system writes the Enter HiddenROM command sequence, it may read the HiddenROM
region by using the addresses normally occupied by the boot sectors. That is, the device sends all commands
that would normally be sent to the boot sectors 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 boot sectors.
The device has a HiddenROM area 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 area is 256 bytes. This area is normally the “outermost” 8 Kbyte boot block area in Bank 1.
Therefore, write the HiddenROM entry command sequence to enter the HiddenROM area. It is called Hidden-
ROM mode when the HiddenROM area appears.
Sectors other than the boot block area SA0 can be read during HiddenROM mode. Read/program of the Hid-
denROM area is possible during HiddenROM mode. Write the HiddenROM reset command sequence to exit
the HiddenROM mode. The bank address of the HiddenROM should be set on the third cycle of this reset
command sequence.
In HiddenROM mode, the simultaneous operation cannot be executed multi-function mode between the Hid-
denROM area and the Bank 1.
To program the data to the HiddenROM area, write the HiddenROM program command sequence during Hid-
denROM 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 area is selected, the previous data will be deleted.
There are two methods to protect the HiddenROM area. One is to write the sector group protect setup command
(60h) , set the sector address in the HiddenROM area and (A
sector group protect command (60h) during the HiddenROM mode. The same command sequence may be used
7
data pooling, DQ
SECTOR-ERASE ARCHITECTURE.)
6
toggle bit and RY/BY pin. You should pay attention to the address to be
70
6
, A
3
, A
2
, A
1
, A
0
)
(0, 0, 0, 1, 0) , and write the
15
to DQ
8
) is “0” in Word