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DS125BR820: EEPROM related questions

daniel
Genius 5095 points
Part Number: DS125BR820

Hi Team,

We use DS125BR820 as a SATA redriver, and use SMB master mode for EEPROM.

1. Could we use one EEPROM shared with 6 re-driver? Is there any concern? One EEPROM is used for 6 re-driver config.

2. Does EEPROM data used by re-driver must be wrote from address 00h? in our case, 00h data may be reserved for other device.

3. Spec. p19,  For transfer rate 1MHz, the redriver exactly access data under 1Mhz? is it workable if we use 400Khz or 100Khz device?

Thanks

  • 0
    TI__Mastermind 43795 points

    Hi Daniel,

    1. Yes it is possible to use a single EEPROM with up to 16 redrivers.

    2. Yes the EEPROM data must start at address 0x00 and the EEPROM must be at address 0xA0

    3. The redrivers do not have an accurate clock to set the I2C rate exactly at 400 KHz.  So in some cases the actual i2C rate will be over 400 KHz when the redriver is acting as the bus master.  For this reason we recommend using a 1 MHz EEPROM. 

    Regards,

    Lee

  • 0 in reply to Lee Sledjeski
    Genius 5095 points

    Hi Lee,

    Thanks for your reply.

    There are another two questions, please help.

    1. As EEPROM maximum size is 8Kbit. Is that meaning we can only use the EEPROM which size smaller than 8Kbit or we can use larger one but re-driver can only access max. 8Kbit size?

    2. Does re-driver’s I2C transaction always read with address byte, like case 2 ?

    Thanks

  • 0 in reply to daniel
    TI__Mastermind 43795 points

    Hi Daniel,

    The SMBus master is limited to address EEPROMs with 8kits or less of address space only.  It is not compatible with larger EEPROMs

    Reading a Register. 

    To read a register, the following protocol is used (see SMBus 2.0 specification).

    1. The Host drives a START condition, the 7-bit SMBus address, and a “0” indicating a WRITE.

    2. The Device (Slave) drives the ACK bit (“0”).

    3. The Host drives the 8-bit Register Address.

    4. The Device drives an ACK bit (“0”).

    5. The Host drives a START condition.

    6. The Host drives the 7-bit SMBus Address, and a “1” indicating a READ.

    7. The Device drives an ACK bit “0”.

    8. The Device drives the 8-bit data value (register contents).

    9. The Host drives a NACK bit “1”indicating end of the READ transfer.

    10. The Host drives a STOP condition.

    The READ transaction is completed, the bus goes IDLE, and communication with other SMBus devices may now

    occur.

    Note: To accomodate EEPROMs >256 Bytes the Register Address will be 2 bytes.

     

    Regards,

    Lee