MIC3000_07 Datasheet, PDF (32/68 Pages) Micrel Semiconductor – FOM Management IC

MIC3000
Micrel
MIC3000 Slave Address
Register Address
1st Data Byte to
MIC3000
2nd Data Byte to
MIC3000
DATA S 1 0 1 0 0 0 0 0 A X X X X X X X X A D7 D6 D5 D4 D3 D2 D1 D0 A D7 D6 D5 D4 D3 D2 D1 D0 • • •
START
R/W = WRITE
ACKNOWLEDGE
ACKNOWLEDGE
ACKNOWLEDGE
CLK
•••
3rd Data Byte to
MIC3000
4th Data Byte to
MIC3000
• • • D7 D6 D5 D4 D3 D2 D1 D0 A D7 D6 D5 D4 D3 D2 D1 D0 /A P
R/W = READ
ACKNOWLEDGE NOT ACKNOWLEDGE
STOP
•••
Master to slave transfer,
i.e., DATA driven by master.
Slave to master transfer,
i.e., DATA driven by slave.
Figure 24. Four-Byte Page_Write Protocol
Acknowledge Polling
The MIC3000’s non-volatile memory cannot be accessed
during the internal write process. To allow for maximum
speed bulk writes, the MIC3000 supports acknowledge poll-
ing. The MIC3000 will not acknowledge serial bus transac-
tions while internal writes are in progress. The host may
therefore monitor for the end of the write process by periodi-
cally checking for an acknowledgement.
Write Protection and Data Security
OEM Password
A password is required to access the OEM areas of the
MIC3000, specifically the non-volatile memory, look-up tables,
and registers at serial addresses A4_h and A6_h. A four-byte
field, OEMPWSET, at serial address A6_h 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 7B_h at serial address A2_h. Therefore, this byte
must be written last! A four-byte burst-write sequence to
address 78_h 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 A2_h. This field is therefore always
visible to the host system. OEMPW is compared to the four-
byte OEMPWSET field at serial address A6_h. If the two fields
match, access is allowed to the OEM areas of the MIC3000
non-volatile memory at serial addresses A4_h and A6_h. If
OEMPWSET is all zeroes, no password security will exist.
The value in OEMPW will be ignored. This helps prevent a
deliberately unsecured MIC3000 from being inadvertently
locked. Once a valid password is entered, the MIC3000 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 regard-
less of the locked/unlocked status of the device. If OEMPWSET
is set to zero (00000000_h), the MIC3000 will remain unlocked
regardless of the contents of the OEMPW field. This is the
factory default security setting.
NOTE: A valid OEM password allows access to the OEM and
user areas of the chip, i.e., the entire memory map, regard-
less 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
MIC3000, specifically the non-volatile memory at serial ad-
dresses A0_h and A2_h. A one-byte field, USRPWSET at serial
address A2_h is used for setting the USER password.
USRPWSET is compared to the USRPW field at serial
address A2_h. If the two fields match, access is allowed to the
USER areas of the MIC3000 non-volatile memory at serial
addresses A0_h and A2_h.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: A valid OEM password allows access to the OEM and
user areas of the chip, i.e., the entire memory map, regard-
less 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. If a valid OEM
password is in place, the user password will have no effect.
M9999-101204
32
October 2004