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AFE031: datasheet and app report clarification needed

Viktorija Cecil
Mastermind 18511 points

Part Number: AFE031

Team, 

AFE031 Data sheet 41 states that:

TX_FLAG output is HI when the transmit signal path is enabled and ready for transmission. Same goes for RX_FLAG

When LO transmit signal path is not enabled. When LO receive signal path is not enabled.

 

Application report SBOA130A states that:

A LO TX_FLAG signals the device is ready for transmission. Same goes for RX_FLAG

TX_FLAG HI signals that the device is not ready for transmission. RX_FLAG HI signals that the device is not ready for reception

 

The data sheet and application report seem to be in disagreement. Do you agree?

 

Can TX_FLAG be used to indicate when a transmission is taking place?

Can RX_FLAG be used to indicate when a reception is taking place?

 

In schematic examples why are these always shown with discrete 33kohm pull-ups? Why not 10k pull-ups?

Thanks

Viktorija

  • 0
    TI__Prodigy 420 points
    Hi Viktorija,

    The datasheet is correct.. pin high and register bit '1' simply indicate that the Tx or Rx block is enabled. That is, they do not indicate a "transmission is taking place", just that the corresponding block is enabled.

    MCUs and FPGAs typically include weak on-chip pull-ups (e.g. 100k) for open-drain inputs. Weaker pull-ups (i.e. higher resistance) require less static current and can be used for slower signals. I suspect this is why the authors of the datasheet/app report chose relatively high pull-up resistors for the Tx and Rx flags.