Siemens MC55 manual Supported character sets, Ira

MC55 AT Command Set

1.5 Supported character sets

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1.5Supported character sets

The ME supports two character sets: GSM 03.38 (7 bit, also referred to as GSM alphabet or SMS alphabet) and UCS2 (16 bit, refer to ISO/IEC 10646). See AT+CSCS for information about selecting the character set. Character tables can be found below.

Explanation of terms

•IRA

IRA means that one byte is displayed as two characters in hexadecimal format. for example, the byte 0x36 (decimal 54) is displayed as "36" (two chars).

•Escape sequences

The escape sequence used within a text coded in the GSM default alphabet (0x1B) must be correctly inter- preted by the TE, both for character input and output. To the module, an escape sequence appears like any other byte received or sent.

•TE

TE is the terminal equipment that uses the GSM default alphabet as its character set. MS Hyperterminal (often used with the module) is an ANSI / ASCII terminal that does not support the GSM default alphabet.

•Data Coding Scheme

The Data Coding Scheme (dcs) is part of a short message and is saved on the SIM. When writing a short message to the SIM in textmode, the dcs stored with AT+CSMP is used.

•TE Character Set

The currently used TE character set is selected with AT+CSCS.

The behavior when encountering characters, that are not valid characters of the supported alphabets, is unde- fined.

Due to the constraints described below it is recommended to prefer the USC2 alphabet in any external applica- tion.

If the GSM alphabet is selected all characters sent over the serial line are in the range from 0 ... 127. CAUTION: GSM alphabet is not ASCII alphabet!

Several problems resulting from the use of the GSM alphabet:

•"@" character with GSM alphabet value 0 is not printable by an ASCII terminal program (e.g. Microsoft© Hyperterminal®).

•"@" character with GSM alphabet value of binary 0 will terminate any C string! This is because the 0 is defined as C string end tag. Therefore, the GSM Null character may cause problems on application level when using a 'C'-function as "strlen()". This can be avoided if it is represented by an escape sequence as shown in the table below.

By the way, this may be the reason why even network providers often replace "@"with "@=*" in their SIM application.

•Other characters of the GSM alphabet are misinterpreted by an ASCII terminal program. For example, GSM "ö" (as in "Börse") is assumed to be "" in ASCII, thus resulting in "Brse". This is because both alphabets mean different characters with values hex. 7C or 00 and so on.

•In addition, decimal 17 and 19 which are used as XON/XOFF control characters when software flow control is activated, are interpreted as normal characters in the GSM alphabet.

When you write characters differently coded in ASCII and GSM (e.g. Ä, Ö, Ü), you need to enter escape sequences. Such a character is translated into the corresponding GSM character value and, when output later, the GSM character value can be presented. Any ASCII terminal then will show wrong responses.

Examples for character definitions depending on alphabet

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