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SN65C3221: Auto Shutdown wake up

setoh waituck
Prodigy 100 points
Part Number: SN65C3221
Other Parts Discussed in Thread: TRS3122E,

Dear Sir/Mdm,

would like to understand how Auto shutdown can be applied,  hope someone can advise.
my question is on Auto Shutdown Mode.
Q.  On two ends of an RS232 link,  if both RS232 devices are configured for Auto Shutdown enabled,  is it possible that both devices are powered off at the same time?
Q.  if yes,  would the DOUT for both devices be "Z" and hence result in the RIN for both devices to be INVALID and lead to the connection unable to be used unless repowered?

thanks and rgds.

  • 0
    TI__Guru 62910 points
    Hi Setoh,

    Our team is looking into this one and will get back to you tomorrow - sorry for the delay.

    Max
  • 0
    TI__Expert 6955 points

    Setoh,

    If both devices have the Auto Shutdown enabled then both can enter the Auto Shutdown mode when there is no more communication activity. This would require the the reset of either device or deactivation of the Auto Shutdown by bringing the FORCEON pin high. Does the application require that both transceivers have the Auto Shutdown feature enabled?

    -Lucas 

  • 0 in reply to Lucas Schulte9
    Prodigy 100 points
    Hi Lucas,
    thanks for the reply.
    my application is such that I cannot rule out that the other transceiver has Auto Shutdown enabled.
    Based on the previous reply, it seems to me that unless my application will never initiate a session, any use of Auto Shutdown parts need an implementation of transceiver reset or control of FORCEON in order to wake up when I transmit.
    alternatively, if AUTOSHUTDOWN PLUS parts are used on my end, can you confirm I will be able to wake up the part when I initiate the session?

    thanks n rgds.
  • 0 in reply to setoh waituck
    TI__Expert 6955 points
    Setoh,

    The Auto Power Down Plus feature functions in a similar way and will have the same limitations as discussed before. You will have to actively wake up at least on of the transceivers .

    -Lucas
  • 0 in reply to Lucas Schulte9
    Prodigy 100 points
    Hi Lucas,
    I've double-checked the auto powerdown plus datasheets below and find the following cited. I've noticed that the Propagation-Delay Times and Supply-Enabling Time diagram for both seems to indicate that the ic will wake up on either Receiver or Driver activity. As such a transmit on my side will wake up my transceiver ic. This would be different from Auto-powerdown which only monitors RX, please comment.

    www.ti.com/.../trs3122e.pdf
    With auto-powerdown plus
    enabled, the device activates automatically when a valid signal change is applied to any receiver or driver input.
    After 30 seconds of inactivity the device will automatically power down to save power.

    www.ti.com/.../trs3253e.pdf
    When a valid transition is sensed on one of the driver or receiver
    inputs, the charge pump turns back on and TRS3122E exits powerdown.

    thanks n rgds, setoh.
  • 0 in reply to setoh waituck
    TI__Mastermind 25705 points
    Setoh,

    Yes. You're right about the function of both devices. The auto power down function is based on the edge detection of input signal in time domain. To distinguish it from the voltage-based one like in SN65C3221, it's called auto power down plus in some datasheet. Please let us know if you have more questions.

    Regards,
    Hao