SIM cards use a protocol based on an Open Systems Interconnection Reference Model.
Tranmission Protocols
-
Information between the SIM and the device is sent via Protocol Data Units (TPDUs), for which there are two common protocols: T=0 and T=1. These protocols differ in the information structure by which the device and SIM card communicate.
-
T=0
The T=0 protocol is a byte-oriented protocol, meaning as little as one byte of information can be transferred in a given transmission. It uses a data structure that is sent from the device to the SIM and back, a process in which it establishes a command and response structure.
T=1
-
T=1 is a protocol that enables blocks of data to be transferred between the SIM card and the device. These blocks are categorized as the supervisory block, information block and receive-ready block. A supervisory block controls data transfer, an information block enables the exchange of data between the SIM card and device application, and a receive-ready block acknowledges (or denies) a received block of information.
yes we can use the sim memory as external memory , in addition to that only certain range of baud rate level it will work if you are assigning with micrcontroller 9600 baud rate is must .