MIC3003 Datasheet, PDF (39/75 Pages) Micrel Semiconductor – FOM Management IC with Internal Calibration

Micrel, Inc.
MIC3003
Figure 24. Eight-Byte Block Write Protocol
Acknowledge Polling
The MIC3003’s non-volatile memory cannot be accessed
during the internal memory update. To allow for maximum
speed bulk writes, the MIC3003 supports acknowledge
polling. The MIC3003 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. The longest duration for the internal
memory update to complete for a block write is
approximately 26 ms.
Write Protection and Data Security
OEM Password
A password is required to access the OEM areas of the
MIC3003, 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 7E_h if
OEMCFG5 bit 2 is set to 1) at serial address A2h.
Therefore, this byte must be written last. A four-byte
burst-write sequence to address 78h (or 7B_h if OEMCFG5
bit 2 is set to 1) may be used as this will result in the
MSbyte being written last. New passwords written to the
OEMPWSET registers 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 MIC3003 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
MIC3003 from being inadvertently locked. Once a valid
password is entered, the MIC3003 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 MIC3003 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.
OEM Mode and User Mode
When the OEM password is unlocked (either by matching
the set password or if the password is all zeros), the
MIC3003 is in OEM Mode. If the part is locked, the part is in
User Mode.
November 2009
39
M9999-111209-C
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