MBM29PL64LM datasheet(29/69 Pages) SPANSION

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MBM29PL64LM90/10

(2) HiddenROM Entry Command

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 / 128 words. This area is in SA0 . Therefore, write the HiddenROM entry

command sequence to enter the HiddenROM area. It is called HiddenROM mode when the HiddenROM area

appears.

Sectors other than the block area SA0 can be read during HiddenROM mode. Read/program of the HiddenROM

area is possible during HiddenROM mode. Write the HiddenROM reset command sequence to exit the Hidden-

ROM 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 com-

mand.

(3) HiddenROM Program Command

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 DQ7 data pooling, DQ6 Toggle bit or RY/BY. You should pay attention to the address to be programmed.

If an address not in the HiddenROM area is selected, the previous data will be deleted.

During the write into the HiddenROM region, the program suspend command issuance is prohibited.

(4) HiddenROM Protect Command

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 (A6, A3, A2, A1, A0)

= (0, 0, 0, 1, 0) , and write the

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 (VID) to A9 and OE, set the sector address in the HiddenROM area

and (A6, A3, A2, A1, A0)

= (0, 0, 0, 1, 0) , and apply the write pulse during the HiddenROM mode. To verify the

protect circuit, apply high voltage (VID) to A9, specify (A6, A3, A2, A1, A0)

= (0, 0, 0, 1, 0) and the sector address

in the HiddenROM area, and read. When “1” appears on DQ0, the protect setting is completed. “0” will appear

on DQ0 if it is not protected. Apply write pulse again. The same command sequence could be used for the above

method because other than the HiddenROM mode, it is the same as the sector group protect previously men-

tioned.

Take note that other sector groups will be affected if an address other than those for the HiddenROM area is

selected for the sector group address, so please be careful. Pay close attention that once it is protected, protection

CANNOT BE CANCELLED.

MBM29PL64LM датащи(PDF) 29 Page - SPANSION