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Original question:

CC1200: The TOC_CFG.TOC_LIMIT setting on CC1200

CC1200: The Bit Synchronization on CC1200

Nomo
Guru 16800 points
Part Number: CC1200
Other Parts Discussed in Thread: WMBUS, , CC1120

Hello,

Please let me confirm the following question.
All of these questions are related to 6.6 Bit Synchronization in user's guide.

1.What is the target of "Symbol Rate Offset Tolerance" in Table 19, a receiver side or a transmitter side?
  Also, does the table show the condition to complete the bit synchronization?

2.What is "Required Preamble Length"?
  Is this the preamble length to complete the bit synchronization in the receiver side?

3.What does mean "0.5 byte (only for gain adjustment)"?
  Is only 0.5 byte needed to complete the bit synchronization and is there any additional re-synchronization?

Best Regards,
Nomo

  • 0
    TI__Guru**** 317180 points

    I believe this post: e2e.ti.com/.../310710 answers some of the questions. Dependent on the datarate variation they have in the system they should select setting accordingly. If they have either < 2 % or < 12 % they should use the TOC_CFG used in the WMBUS S or T mode settings.

    The 12 % setting works on CC1120/5 but I have not found any settings that gives 0 % PER with 12 % for CC1200. 


    1) This is on the recieve side.

    2) For TOC_CFG.TOC_LIMIT > 0, the preamble length has to be 4 bytes or more.

    3) Yes, TOC_CFG.TOC_LIMIT = 0 and when not using zero IF 4 bit preamble is enough to settle the AGC. Bit and byte sync is done in the sync word.

  • 0
    TI__Mastermind 39860 points
    Generally: The preamble is needed to set up the correct AGC gain and do bit synchronization

    1) Symbol rate offset is the difference between the TX and RX data rates.
    If you use CC1200 in RX the data rate offset in RX will be set by the crystal tolerance (ppm) and the finite resolution of the data rate programming (see equation in the user guide). Even when accounting for both of these the total RX data rate offset will be very low.
    If you use CC1200 in TX the data rate offset will be the same as for RX. The total offset will be much less than <0.2% and TOC_LIMIT = 0 should be used.
    If you have a legacy transmitter with a larger data rate offset you need to configure the CC1200 receiver to account for the offset introduced by the transmitter.
    The preamble length in Table 19 is the required length to do AGC gain adjustment and bit synchronization.

    2) Yes (in addition to setting up the AGC gain)

    3) When TOC_LIMIT = 0 only 4 bits of preamble is needed for setting up the correct AGC gain and do bit synchronization (note: assuming the offset is less than 0.2%).