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CDCM6208: datasheet changed from rev E to rev G regarding how to transition from pin mode to host mode

james garrett
Prodigy 160 points
Part Number: CDCM6208

The rev E of the datasheet states the following:

A system may transition a device from pin mode to host connected mode by changing the state of the SI_MODE pins and then triggering a device reset (either via the RESETN pin or via setting the RESETN bit in the device registers).


The newest rev G states something different:

A system may transition a device from pin mode to host connected mode by changing the state of the SI_MODE pins and then triggering a device power cycle by toggling the PDN input pin (high-low-high)


Please explain which method is correct or if both methods work and why the datasheet was changed.  I am trouble-shooting a system with intermittent problems that followed the procedure in the Rev E datasheet.  This system does not provide control of the PDN input; it is a no connect.  Given this how can I transition from pin mode to host (SPI) mode ?

  • 0
    TI__Genius 16845 points
    Hello,

    I don't have the full history surrounding the datasheet change, but I will try to help here.

    I believe the second method is correct. It matches the flow chart given in Figure 35 which indicates that PDN must be changed to change from pin mode to host mode.

    Figure 35 was not changed between revisions. The datasheet statement was probably an erratum that was not corrected until Rev F.

    You would need to toggle PDN to transition from pin mode to host mode. The alternative would be to initiate a power-on reset with the correct settings on SI_MODE[1:0].

    Kind regards,
    Lane
  • 0 in reply to Lane Boyd
    Prodigy 160 points

    In our application we power up in pin mode and a few seconds later we transition to SPI mode to disable unused outputs to reduce power.   The system does not have access to the PDN input and we have been following the rev E datasheet by changing the SI_MODEx pins to indicate SPI,  followed by RESET held low,  followed by writes over the SPI interface.  This has been working fine as we see the unused outputs turn off as expected and the intended outputs retain their settings from the initial pin mode.    Is there any problem or risk with using this method ?     

  • 0 in reply to james garrett
    TI__Mastermind 27581 points
    James,

    I'm going to notify another engineer of this.

    Given it's the holiday season coming and there might be delayed response, here's my shot at this.

    For some other devices in our group (i.e. LMX2615), we also have pin modes that are applied on the initial power on reset. However, you can overwrite parts of the pin mode, specifically turning outputs on/off.

    The CDCM6208 is a different part, but I would think it would be similar, although you can't take my response to the bank.

    Regards,
    Dean