LTC2995 datasheet(24/90 Pages) AD

24 / 90 page

LTM2985

Rev. 0

For more information www.analog.com

EEPROM OVERVIEW

The LTM2985 contains 512 bytes of EEPROM, which

shadowstheuppersensorconfigurationsegmentofUSER

RAM (locations 0x200–0x3CF, see Figure 4). Prior to initial

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

LTM2985 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

2985 F04

Figure 5. EEPROM Write Operation

EEPROM WRITE OPERATION

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

1. Sensor Configuration. Write all desired channel as-

signment and custom sensor data to the LTM2985

USER RAM.

2. Set EEPROM Key. Write the EEPROM Key

(0xA53C0F5A) to the key register space of the

LTM2985 USER RAM (Address range 0x0B0–0x0B3,

see Table 11). Note the key is written MSB first.

3. SendEEPROMWriteCommand.WritetheEEPROMwrite

command (0x15) and start bit (0x80) to the LTM2985

commandregister(Address0x000).Thecommandplus

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

4. WaitforEEPROMCommandtoComplete.Completion

of the write operation is indicated by both the INT pin

going HIGH and the status register START bit going

LOW and DONE bit going HIGH.

5. CheckEEPROMStatusRegister.ReadEEPROMStatus

Failed status bit (Bit 2) to determine whether the EE-

PROM write operation was successful (see Table 13).

The Program-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

using a 32-bit checksum, which covers the entire contents

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

reporting ECC status and checksum error conditions.

2985 F05

WRITE EEPROM KEY

TO LTM2985

CHECK EEPROM

STATUS REGISTER

DONE

USER DEFINED

EEPROM

ERROR HANDLER

SEND EEPROM WRITE COMMAND

(COMMAND 21)

WAIT FOR EEPROM

COMMAND TO COMPLETE

LTM2985

READY

WRITE CHANNEL ASSIGNMENT

AND CUSTOM SENSOR DATA

TO LTM2985

ELSE

PROGRAM FAILED

STATUS BIT SET

LTC2995 Datasheet(PDF) 24 Page - Analog Devices

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