Requirements For Using The Ccin Pin - Siemens MC45 Manual

MC45 Hardware Interface Description
P R E L I M I N A R Y

3.7.1 Requirements for using the CCIN pin

The module's startup procedure involves a SIM card initialization performed within 1 second
after getting started. A most important issue for reliable operation is whether the initialization
procedure ends up with a high or low level of the CCIN signal:
a) If, during startup of MC45, the CCIN signal on the SIM interface is high, then the status
of the SIM card holder can be recognized each time the card is inserted or ejected. This
can be easily achieved when the card holder comprises a card detect switch. The switch
causes CCIN to go and stay high when the card is present.
A low level of CCIN indicates that the holder is empty. In this case, the module keeps
searching, at regular intervals, for the SIM card. Once the card is inserted, CCIN is taken
high again.
b) If, during startup of MC45, the CCIN signal is low, the module will also attempt to
initialize the SIM card. In this case, the initialization will only be successful when the card
is present.
If the SIM card initialization has been done, but the card is no more operational or
removed, then the module will never search again for a SIM card and only emergency
calls can be made.
It is strongly recommended to connect the contacts of the SIM card detect switch to the
CCIN input and to the CCVCC output of the module as illustrated in the sample diagram in
Figure 20. The additional switch in the CCIN line shown in Figure 20 is intended for
debugging purposes only and is, normally, not required in your application.
In special cases, the CCIN signal might be controlled by the host application. If so, be sure
that the CCIN signal is low while the output voltage VDD is low, too. In particular, no voltage
may be applied at the CCIN input, when MC45 is in POWER DOWN mode. Otherwise,
proper operation of MC45 may be affected due to an electric leakage current flowing through
the CCIN pin into the module.
MC45_HD_01_V00.02a Page 54 of 90 12.08.2002