LTC2984 datasheet(23/78 Pages) AD

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LTC2984

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EEPROM OVERVIEW

The LTC2984 contains 512 bytes of EEPROM, which

shadowstheuppersensorconfigurationsegmentofUSER

RAM(locations0x200–0x3CF,seeFigure4).Priortoinitial

usage, the user programs the USER RAM with all channel

assignment and custom sensor data. Once the USER RAM

has been programmed, the user can save this segment of

memory into the EEPROM. After subsequent power down

orsleepcycles,theusercanreloadtheUSERRAMwiththis

stored EEPROM data bypassing the channel assignment

and customer sensor programming normally required.

APPLICATIONS INFORMATION

Figure 4. Shadow EEPROM Memory Map

BYTE

ADDRESS

0000

01FF

0200

03CF

03DO

03FF

LTC2984 SPI

ADDRESS SPACE

USER COMMAND

REGISTERS,

RESULTS DATA,

GLOBAL CONFIGURATION

AND STATUS

SENSOR CONFIGURATION

MEMORY SEGMENT

(CHANNEL ASSIGNMENT

AND

CUSTOM SENSOR DATA)

COMMAND 21

(0x15)

COMMAND 22

(0x16)

EEPROM

SHADOW

RESERVED

RESERVED*

*NOTE: 03D0–03FF IS RESERVED

AND IS NOT SHADOWED BY EEPROM

2984 F04

Figure 5.

2984 F05

WRITE EEPROM KEY

TO LTC2984

CHECK EEPROM

STATUS REGISTER

DONE

USER DEFINED

EEPROM

ERROR HANDLER

SEND EEPROM WRITE COMMAND

(COMMAND 21)

WAIT FOR EEPROM

COMMAND TO COMPLETE

LTC2984

READY

WRITE CHANNEL ASSIGNMENT

AND CUSTOM SENSOR DATA

TO LTC2984

ELSE

PROGRAM FAILED

STATUS BIT SET

EEPROM WRITE OPERATION

The EEPROM write operation requires 5 steps (see Figure 5).

1. Sensor-Configuration.Writealldesiredchannelassignment

and custom sensor data to the LTC2984 USER RAM.

2. SetEEPROMKey.WritetheEEPROMKey(0xA53C0F5A)

to the key register space of the LTC2984 USER RAM

(Address range 0x0B0–0x0B3, see Tables 5, 7 and 11).

Note the key is written MSB first.

3. SendEEPROMWriteCommand.WritetheEEPROMwrite

command (0x15) and start bit (0x80) to the LTC2984

command register (Address 0x000). The command plus

start bit is 0x80 + 0x15 = 0x95 (see Table 12).

4. Wait for EEPROM Command to Complete. Completion

of the write operation is indicated by both the interrupt

pin going HIGH and the status register START bit going

LOW and DONE bit going HIGH.

5. Check EEPROM Status Register. Read EEPROM Status

status bit (Bit 2) to determine whether the EEPROM write

operationwassuccessful(seeTable13).TheProgram-Failed

status bit being set indicates that the write operation failed.

Upon successful completion of steps 1–5, the EEPROM

will now contain the image that was present in USER RAM

locations 0x200–0x3CF.

EEPROM READ/WRITE VALIDATION

Access to the EEPROM is key-protected to prevent inad-

vertent access. The EEPROM also has two levels of data

integrity protection. The first level is implemented using

an error correcting code (ECC) on each 32-bit word of

data in the EEPROM. The ECC is capable of correcting

any single bit error per word and detecting 2-bit errors

per word. The second level of protection is implemented

usinga 32-bitchecksum,whichcoverstheentirecontents

of user EEPROM. Status bits are available to the user for

reporting ECC status and checksum error conditions.

LTC2984 Datasheet(PDF) 23 Page - Analog Devices

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