The Universal Integrated Circuit Card (UICC) interface can be tested by controlling the UICC pins with the %XGPIOTEST AT command and checking the pin states.
Each pin in the UICC interface can be set to the output mode and to the logic low state (0 V) or to the logic high state (1.8 V). The pins are SIM_RST (pin 16), SIM_CLK (pin 18), SIM_IO (pin 17), and SIM_1V8 (pin 19). The pin voltage can then be measured with external test equipment. Alternatively, the pins can be set to the input state and the pin status can be read. The result of the test can be compared to an externally set level. Some of the UICC pins are unidirectional, supporting testing only in a predefined mode.
For information on each pin’s control options and the %XGPIOTEST AT command, see Modem GPIO functionality test %XGPIOTEST in nRF91x1 Production Test AT Commands Reference Guide.