Datasheet

MSL2021 [DATASHEET]

42062A–LED–02/2013

12.1 EEPROM and Power-Up Defaults

An on-chip EEPROM holds all the default register values. At power-up the data in the EEPROM is transferred directly to

control registers 0x00 thru 0x51, setting up the device for operation.

Any changes made to registers 0x00 thru 0x69 after power-up are not reflected in the EEPROM and are lost when power

is removed from the device, or when the enable input EN is forced low. If a different power-up condition is desired

program the values into the EEPROM via the serial interface as explained in the next section, or contact the factory to

inquire about ordering a customized power-up setting.

12.2 EEPROM Address and Control/Status Registers

The EEPROM can be visualized as an image of the control registers from 0x00 thru 0x69. Change an EEPROM register

value by writing the new value into the associated control register, and then instructing the device to program that value

into the EEPROM. Two control registers facilitate this process, the EEPROM address register E2ADDR (0x60), and the

EEPROM control register E2CTRL (0x61). Into E2ADDR write the location of the data that is to be programmed into the

EEPROM, and write 0x03 to E2CTRL to command the device to program that data into the EEPROM. Programming the

EEPROM takes a finite amount of time; after sending a command to E2CTRL wait 5ms, then end the write cycle by

writing 0x00 to E2CTRL.

Example: Change the string current feedback voltage MREF to 100mV.

Commands: To register 0x20 (MREF) write 0x32 (the new value for MREF). To register 0x60 (E2ADDR) write 0x20 (the

address of the MREF register). To register 0x61 (E2CTRL) write 0x03 (the command to copy the value to EEPROM).

Wait 5ms. To register 0x61 (E2CTRL) write 0x00, to turn off EEPROM access.

Result: The value 0x32, located in the MREF register, is programmed into the EEPROM and becomes the new power-

up default value for MREF.

Summary:

0x20 32

0x60 20

0x61 03

Wait 5ms

0x61 00

E2CTRL provides additional functions beyond simply programming a register’s value into the EEPROM. Data may be

transferred in either direction, from the registers to the EEPROM, or from the EEPROM to the registers. Register data

may be transferred into or out of the EEPROM in groups of eight, a page at a time. The page address boundaries are

predefined, and E2ADDR must be loaded with the address of the first byte of the page that is to be copied. Page

addresses begin at 0x00 and increment by eight, with the second page beginning at 0x08, the third at 0x10, etc. To

program a full page of data into the EEPROM, write the address of the page’s first byte to E2ADDR, and write 0x04 to

E2CTRL. Wait 5ms, and then end the write cycle by writing 0x00 to E2CTRL. When finished accessing the EEPROM

always write 0x00 to E2CTRL to block inadvertent EEPROM read/writes. Table 12-2 on page 26 details the functions

available through E2CTRL.

Table 12-2. EEPROM Address Register (E2ADDR, 0x60), defaults highlighted.

D7 D6 D5 D4 D3 D2 D1 D0

E2ADDR 0x60 - E2ADDR[6:0]

DEFAULT 00000000

EEPROM Minimum Address 0x00

-0000000

EEPROM Maximum Address 0x51

-1010001