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Does CC2480 need the XTAL2 crystal when operating in UART mode?

sumsar
Prodigy 70 points
Other Parts Discussed in Thread: CC2480A1, SN75176B

Is mounting the XTAL2 (ref.: page 20, http://focus.ti.com/lit/ds/symlink/cc2480a1.pdf) crystal a waste (of money) when operating in UART mode? The processor can not enter low power state when running in UART mode, as I understand it.

 

  • 0
    TI__Expert 4155 points

    I assume you're talking about the external 32kHz for power savings. Since UART mode doesn't support power savings, yes this crystal would be redundant if you were using uart mode.

  • 0 in reply to "Double 0"
    Prodigy 70 points

    Ok.

    Now, if we assume that we have a system with a RS485 bus, would it then be possible (probably with a few CTS/RTS related tricks) to connect the cc2480 to this bus using a differential bus tranceiver like this one from you: http://focus.ti.com/lit/ds/symlink/sn75176b.pdf ?

  • 0 in reply to sumsar
    TI__Guru 63205 points

    Using something like a CTS/RTS based system, would provide the ability to use this edge to wake up the device, provided it is connected to one of the I/Os which has external interrupt capability.  This could be used to wake up the device.

  • 0 in reply to BrandonAzbell
    Prodigy 70 points

    One way to "force" the cc2480 to a half-duplex is to raise CTS (trigger on startbit (and other 1s) and stay high for the dureation of a byte) when it gets data on the line and also to let the startbit (and other 1s) of a transmission enable the rs485 driver/disable the receiver (also for the duration of a byte).