11.123GPPSpecification on the 3 volt subscriber identity module Equipment (SIM-ME) InterfaceTS
4.1 3V technology SIM
The SIM shall operate on both 5V ± 10% according to GSM 11.11 (ETS 300 608) , and on 3V ± 10% according to this ETS. If the ME supplies 5V to the SIM, both the ME and the SIM shall operate according to GSM 11.11 (ETS 300 608) . The logical operation of the 3V technology SIM shall be as defined in GSM 11.11 (ETS 300 608) .
Clock stop mode shall be supported by the SIM. The SIM shall indicate "Clock Stop Allowed" in the file characteristics of the status information as specified in GSM 11.11 (ETS 300 608) .
4.2 3V technology impact
When supplied with the supply voltage as specified in this ETS the SIM shall be operated with a clock frequency of 1 to 4 MHz.
4.3 3V technology SIM Identification
The 3V technology SIM shall contain an identification. The identification is coded on bit 5 in byte 14 of the status information as follows:
"0" : 5V only SIM;
"1" : 3V technology SIM.
In the case that the ME offers full compatibility by being able to operate the SIM interface at both 3V and 5V, then bit 5 in byte 14 of the status information, when set to “1”, indicates that the SIM may be operated at 3V.
The procedure for deriving the identification bit shall be performed by the ME immediately after the Answer To Reset (ATR) and before issuing any other command. The procedure consists of the two commands "SELECT GSM" and "STATUS/GET RESPONSE"
4.4 3V technology ME
The 3V technology ME shall initially activate the SIM with 5V according to GSM 11.11 (ETS 300 608) . If the SIM indicates 3V operation as defined in subclause 4.3, the ME may switch to 3V operation as defined in subclause 4.7. If switching is performed it shall take place before issuing any further commands.
4.5 3V Only ME
The 3V only ME activates the SIM at 3V.
If the ME is able to detect a 5V only SIM according to the procedure in subclause 4.3, or if the procedure cannot be completed, the ME shall deactivate and reject the SIM immediately (maximum of 5s) without issuing any further command. This rejection ensures that a SIM which appears to operate successfully during these early procedures is not allowed to continue further into the GSM session where it may subsequently give unreliable operation at 3V.
If an ATR is corrupted or not received by the ME, error handling according to clause 5.10 of GSM 11.11 (ETS 300 608)  shall apply.
4.6 Activation and deactivation
The ME shall connect, activate and deactivate the SIM in accordance with the operating procedures specified in GSM 11.11 (ETS 300 608)  taking into account the electrical characteristics specified in clause 5 of this ETS. In particular, Vcc is powered when it has a value between 2,7 V and 3,3 V.
4.7 Supply voltage switching
MEs supporting both 3V and 5V operation may switch between the two supply voltages. Switching shall always be performed by deactivating the SIM and activating it at the new supply voltage. Activation and deactivation of the SIM with 5V shall be according to GSM 11.11 (ETS 300 608) , whereas activation and deactivation of the SIM with 3V shall be according to this ETS.
4.8 Cross compatibility
Cross compatibility means that the ME supports 3V and 5V operation. This is, however, optional for the ME. In case of the 3V technology ME, full cross compatibility is provided, whereas, a 3V only ME requires a 3V technology SIM for operation. However, the 3V technology SIM (see definitions) ensures full cross compatibility.
Due to technology development it is possible in the future, when sub-micron technology is introduced, that Integrated Circuits (ICs) used in MEs may not withstand the 5V supply voltage. This may, in particular, be the case for ICs operating in the power supply range of 1,5V to 3,6V. It may therefore be necessary in the future to specify a low voltage only SIM interface.
NOTE: When a low voltage only SIM is inserted into an ME when it is supplying 5V, the SIM may be destroyed which in some cases could cause permanent damage to the ME. Precautions should be taken by the IC manufacturers to prevent the low voltage ICs from being damaged at 5V.