LMX2491: 40bit data transfer

Shuji Ishiwata

Part Number: LMX2491
Other Parts Discussed in Thread: LMX2572

Hi All,

I have a question about the LMX2491.

Please tell me how to send 40bit as described below.

I understand that if LE is not rise, 40-bit data (5 registers) can be sent to the next lower register.
is my understanding correct?

Also, do you have materials such as the bit configuration for reading and the bit configuration for writing?

Best Regards,
Ishiwata

0 Noel Fung over 2 years ago

Hi Ishiwata-san,

This is called block programming.

We have the following description in LMX2572 datasheet. Same applies to LMX2491.

0 Shuji Ishiwata over 2 years ago in reply to Noel Fung

Hi Noel-san,

Thanks for your answer.

The LMX2572 has an ADD_HOLD pin, but the LMX2491 does not.

If the ADD_HOLD pin is not used, should CSB be held low to maintain Block Programming?

Or do you need the ADD_HOLD pin?

Best Regards,
Ishiwata

0 Noel Fung over 2 years ago in reply to Shuji Ishiwata

Hi Ishiwata-san,

These are two different devices, their register maps are not the same.

LMX2491 was design to support block programming by default.

0 Shuji Ishiwata over 2 years ago in reply to Noel Fung

Hi Noel-san,

Thanks for your answer.

For the LMX2572, data is incremented from higher register addresses to lower numbers.
For example, R20→R19→R18→R17→...

Is it the same for the LMX2491? Please tell me the order of the register address of the data to be incremented.

Thank you for your support.

Best Regards,
Ishiwata

0 vicente flores prado over 2 years ago in reply to Shuji Ishiwata

Hi Shuji-san,
Yes. It's the same for LMX2491. Device registers are programmed in reverse order, i.e. R[n], R[n-1], ... , R[1], R[0].

Regards,

Vicente

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