BG95-M3 and USIM card slot

I’m using a BG95-M3 modem. I’m having issues with the SIM card identification (I’m not using (U)SIM card detection pin), when I’m trying to perform network registration I get SIM errors “(U)SIM failure” and “(U)SIM not inserted”. The behavior I noticed was: when the modem turns on the USIM_VDD, USIM_RST and USIM_DATA get high(1.8v) for a few seconds and then stay always 0v. Is this behavior normal? What does it mean?
Best Regards and Thank you

  1. based on your description , your sim card has not been detected normally
    pls check the below point:

a. pls checking the voltage type of your SIm card , is it 3.3v ,or 1.8v
for BG95 we support 1.8v sim only
b,pls design your sim HW with the below reference circuit

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Hi Stephen,
a) The voltage of SIM is correct;
b) the interface circuit is correct too, I’m not using the Parasitic capacitance and the R1003––R1005 resistance to facilitate debugging; Do you think this is a problem?

Then, the modem behavior, putting 1.8v volts in the data and vdd and clk USIM lines and then going to 0v is the correct behavior? If yes, then the modem is correct, what could be?

Thank you