External SIM card holder

  • Question:
    Can the customer design the application is such a way that they
    can change from the internal sim card to the external and back to
    the internal without turning off the GM862 modem?


    Answer:
    The GM862 don`t permit that internal SIM and external SIM are simultaneously
    inserted.


    A solution could be this one:
    You must use two external SIM card Holder and add two three states buffers
    to separate the not active SIM from the bus of active SIM.


    On the GM862 there is a CCIO line for managing the inserting and removing of
    the external SIM card Holder.
    The CCIO pin must be managed from an external logic control in such a way
    that:


    1- at the ignition of GM862 the SIM must be inserted and the CCIO pin must
    be low.
    2- when you need to change SIM you must switch the CCIO pin high
    3- to set in tristate the buffer of SIM that you want disable.
    4- to activate the buffer of the SIM you want to use
    5- you must put the CCIO pin low again.
    6- now the GM862 starts with the SIM inizialization again


    Note: There is no limit about number of SIMs, obviously you have to use the
    same number of SIM and three state buffers.