Micrel, Inc.
MIC3001
August 2004
54
M9999-082404-A
OEM Password Entry (OEMPW)
D[7]
read/write
D[6]
read/write
D[5]
read/write
D[4]
read/write
D[3]
read/write
D[2]
read/write
D[1]
read/write
D[0]
read/write
Default Value
0000 0000b = 00h (reset to zero at power-on)
Serial Address
A2h = 1010001b
Byte Address
120 – 123 = 78h - 7Bh
(MSB is 7Bh)
This four-byte field is for entry of the password required to access the OEM area of the MIC3001’s memory and registers. A
valid OEM password will also permit access to the user areas of memory. The byte at address 123 (7Bh) is the most significant
byte. This field is compared to the four-byte OEMPWSET field at serial address A6h, bytes 12 to 15. If the two fields match,
access is allowed to the OEM areas of the MIC3001 non-volatile memory at serial addresses A4h and A6h. The OEM password
is set by writing the new value into OEMPWSET. The password comparison is performed following the write to the MSB,
address 7Bh. This byte must be written last!
A four-byte burst-write sequence to address 78h 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. This 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 MIC3001 will remain unlocked regardless of the contents of the OEMPW field. This is the factory default
security setting.
Byte
Weight
3
OEM Password Entry, Most Significant Byte (Address = 7Bh)
2
OEM Password Entry, 2nd Most Significant Byte (Address = 7Ah)
1
OEM Password Entry, 2nd Least Significant Byte (Address = 79h)
0
OEM Password Entry, Least Significant Byte (Address = 78h)
USER Password Setting (USRPWSET)
D[7]
read/write
D[6]
read/write
D[5]
read/write
D[4]
read/write
D[3]
read/write
D[2]
read/write
D[1]
read/write
D[0]
read/write
Default Value
0000 0000b = 00h
Serial Address
A2h = 1010001b
Byte Address
250 = FAh
This register is for setting the password required to access the USER area of the MIC3001’s memory and registers. This field is
compared to the USRPW field at serial address A2h, byte 251. If the two fields match, access is allowed to the USER areas of
the MIC3001 non-volatile memory at serial addresses A0h and A2h. If a valid USER password has not been entered, writes to
the serial ID fields, USRCTRL, and the user scratchpad areas of A0h and A2h will not be allowed, and USRPWSET will be
unreadable (returns all zeroes).
A USER password is set by writing the new value into USRPWSET. 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. This register is non-volatile and will be maintained through power and reset cycles. A valid USER or OEM
password is required for access to this register. Otherwise, this register will read as 00h. Note: a valid OEM password overrides
the USER password setting. If a valid OEM password is currently in place, the user password will have no effect.