Datasheet

23
MSL2021 [DATASHEET]
42062A–LED–02/2013
11.9 MSL2021 Look-Up Table Lockout Procedure
The MSL2021 features a lock for the look-up table. When locked, the table’s registers (0x00 through 0x1F) become read-
only. A locked table cannot be unlocked; changing the table’s registers is no longer possible. Reads of a locked table’s
registers return 0x00, unless the password (chosen when locking the table) is first entered to make the registers visible.
Locking the table requires use of the I
2
C interface to enter data, read data and program the EEPROM. For information
about using the I
2
C interface, see “I²C Serial Interface ” on page 31. For information about programming the EEPROM
see “EEPROM Address and Control/Status Registers” on page 26.
Lock the table by performing the following sequence; an example is presented below:
1. Fill the look-up table with data.
2. Commit the look-up table to EEPROM.
3. Cycle power, then verify the contents of the look-up table.
4. Choose a 16-bit password.
5. Enter the password into Password Registers 0x68 and 0x69.
6. Enter the password into Password Verification Registers 0x38 and 0x39.
7. Commit the password to EEPROM.
8. Set the lock bit.
9. Commit the lock bit to EEPROM.
10. Cycle power to the MSL2021.
11.9.1 Example:
The Look-Up Table is four pages long (each page is 8-bytes). When the look-up table is filled with the proper data,
commit the data to the EEPROM, one page at a time, by sending the following commands to the MSL2021 through its
I
2
C interface:
0x60 0x00 {to register 0x60 write 0x00: sets the EEPROM write pointer to 0x00}
0x61 0x04 {to register 0x61 write 0x04: writes the first page (8 bytes) of data to the EEPROM}
Wait 5ms.
0x61 0x00 {to register 0x61 write 0x00 : disables EEPROM writing}
0x60 0x08 {sets the EEPROM write pointer to 0x08}
0x61 0x04 {writes the second page of data to the EEPROM}
Wait 5ms.
0x61 0x00 {disables EEPROM writing}
0x60 0x10 {sets the EEPROM write pointer to 0x10}
0x61 0x04 {writes the third page of data to the EEPROM}
Wait 5ms.
0x61 0x00 {disables EEPROM writing}
0x60 0x18 {sets the EEPROM write pointer to 0x18}
0x61 0x04 {writes the final page of data to the EEPROM}
Wait 5ms.