MIC3002 datasheet(39/65 Pages) MICREL

39 / 65 page

Micrel, Inc.

MIC3002

July 2007

M9999-073107-B

hbwhelp@micrel.com or (408) 955-1690

Figure 24. Four-Byte Page White Protocol

Acknowledge Polling

The MIC3002’s non-volatile memory cannot be accessed

during the internal write process. To allow for maximum

speed bulk writes, the MIC3002 supports acknowledge

polling. The MIC3002 will not acknowledge serial bus

transactions while internal writes are in progress. The host

may therefore monitor for the end of the write process by

periodically checking for an acknowledgement.

Write Protection and Data Security

OEM Password

A password is required to access the OEM areas of the

MIC3002, specifically the non-volatile memory, look-up

tables, and registers at serial addresses A4h and A6h. A four-

byte field, OEMPWSET, at serial address A6h is used for

setting the OEM password. The OEM password is set by

writing OEMPWSET with the new value. The password

comparison is performed following the write to the MSB of

the OEMPW, address 7Bh (or 7Eh) at serial address A2h.

Therefore, this byte must be written last. A four-byte burst-

write sequence to address 78h (or 7Bh) may be used as this

will result in the MSB being written last. The new password

will not take effect until after a power-on reset occurs or a

warm reset is performed using the RST bit in OEMCFG0.

This allows the new password to be verified before it takes

effect.

The corresponding four-byte field for password entry,

OEMPW, is located at serial address A2h. This field is

therefore always visible to the host system. OEMPW is

compared to the four-byte OEMPWSET field at serial

address A6h. If the two fields match, access is allowed to the

OEM areas of the MIC3002 non-volatile memory at serial

addresses A4h and A6h. If OEMPWSET is all zeroes, no

password security will exist. The value in OEMPW will be

ignored. This helps prevent a deliberately unsecured

MIC3002 from being inadvertently locked. Once a valid

password is entered, the MIC3002 OEM areas will be

accessible. The OEM areas may be re-secured by writing an

incorrect password value at OEMPW, e.g., all zeroes. In all

cases, OEMPW must be written LSB first through MSB last.

The OEM areas will be inaccessible following the final write

operation to OEMPW’s LSB. The OEMPW field is reset to all

zeros at power on. Any values written to these locations will be

readable by the host regardless of the locked/unlocked status

of the device. If OEMPWSET is set to zero (00000000h), the

MIC3002 will remain unlocked regardless of the contents of the

OEMPW field. This is the factory default security setting.

Note that a valid OEM password allows access to the OEM

and user areas of the chip, i.e., the entire memory map,

regardless of any user password that may be in place. Once

the OEM areas are locked, the user password can provide

access and write protection for the user areas.

User Password

A password is required to access the USER areas of the

MIC3002, specifically, the non-volatile memory at serial

addresses A0h and A2h. A one-byte field, USRPWSET at serial

address A2h is used for setting the USER password.

USRPWSET is compared to the USRPW field at serial address

A2h. If the two fields match, access is allowed to the USER

areas of the MIC3002 non-volatile memory at serial addresses

A0h and A2h. The USER password is set by writing

USRPWSET with the new value. The new password will not

take effect until after a power-on reset occurs or a warm reset

is performed using the RST bit in OEMCFG0. This allows the

new password to be verified before it takes effect.

Note also that a valid OEM password allows access to the

OEM and user areas of the chip, i.e., the entire memory map,

regardless of any user password that may be in place. Once

the OEM areas are locked, the user password can then provide

access and write protection for the user areas. If a valid OEM

password is in place, the user password will have no effect.

MIC3002 Datasheet(PDF) 39 Page - Micrel Semiconductor

MIC3002 Datasheet(HTML) 39 Page - Micrel Semiconductor

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