LMX2594: MASH_SEED increment applied when writing register

Variac996

Part Number: LMX2594

Hello.

The datasheet explains the MASH_SEED register in Table 27:

The initial state of the MASH engine first accumulator. Can be used to shift phase or optimize fractional spurs. Every time the MASH_SEED field is programmed, it ADDS this MASH seed to the existing one. To reset it, use the MASH_RESET_N bit.

Since there are actually two MASH_SEED registers (R40) and (R41) for the LSB and MSBs, is the mash seed applied when writing to R40 or when writing R41?

Looking at your (excellent) TICS Pro software, when I write a MASH_SEED it writes R40 first, then R41. The datasheet in 7.5.1 (Recommended Initial Power-Up Sequence) says to write the registers in reverse order though.

Please could you let me know in which order I should be writing R40 and R41 to apply the MASH_SEED value.

Thanks

over 7 years ago

0 Simon Damphousse over 7 years ago

TI__Expert 5370 points

Dear Variac,

good question. R40 is MSB, R41 is LSB. The one time load into the accumulator occurs on R41. for both R40 and R41. When you write R40, you then need to write R41 to do the one time load.

Programming sequence from top to bottom is not quite right wrt these two registers. Good catch.

Regards, Simon.

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LMX2594: MASH_SEED increment applied when writing register