MIC3003GML datasheet(39/75 Pages) MICREL

39 / 75 page

Micrel, Inc.

MIC3003

November 2009

M9999-111209-C

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

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

periodically

checking

for

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 7Eh 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 7Bh 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.

MIC3003GML 数据表(PDF) 39 Page - Micrel Semiconductor

MIC3003GML 数据表(HTML) 39 Page - Micrel Semiconductor

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75

数据表下载