User`s guide

Chapter 1 – AT Commands for Remote SIM Application Toolkit
Multi-Tech Systems, Inc. SIM Application Toolkit AT Commands (S000391C) 7
1.1.6 Parameter Types
Strings are passed as UCS2 characters, but using the GSM alphabet is also possible. It should be mentioned that the
use of the GSM alphabet is not recommended since a SIM can contain text which might not be able to be displayed;
e.g., Greek characters.
To select the type of alphabet, use the AT^SSTA command. The type is determined both for inputs and outputs.
UCS is specified in ISO/IEC 10646. There are 2 and 4 octet versions available; however, only the 2-octet variant
(known as UCS2) is used.
The 65536 positions in the 2-octet form of UCS are divided into 256 rows, each with 256 cells. The first octet of a
character representation gives the row number; the second, the cell number. The first row (row 0) contains exactly
the same characters as ISO/IEC 8859-1. The first 128 characters are the ASCII characters.
The octet representing an ISO/IEC 8859-1 character is easily transformed to the representation in UCS by putting a 0
octet in front of it. UCS includes the same control characters as ISO/IEC 8859 and are located in row 0.
Example:
’<x><x><n><n>’
<x><x> specifies the character set.
<n><n> specifies the character.
1.1.7 States of Remote SAT
In order to communicate with the SIM Application Toolkit it is necessary to use AT commands; these commands are
explained in detail in the following chapters.
In general, the type of AT command which should be issued depends on the current state of the Remote-SAT
interface.
The current state of the Remote-SAT is determined by:
1. The application running on the SIM,
2. The application running on the TA (external controller),
3. The internal actions of the ME (especially SAT and Call Control).