Iec 61131-3 Second edition 2003-01 Programmable controllers – Part 3: Programming languages
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- 2.1.2 Identifiers
2 Common elements
This clause defines textual and graphic elements which are common to all the programmable controller programming languages specified in this Part of IEC 61131. 2.1 Use of printed characters 2.1.1 Character set Textual languages and textual elements of graphic languages shall be represented in terms of the “ISO-646 IRV” given as table 1 - Row 00 of ISO/IEC 10646-1. The use of characters from additional character sets, for example, the “Latin-1 Supplement” given as table 2 - Row 00 of ISO/IEC 10646-1, is a typical extension of this standard. The encoding of such characters shall be consistent with ISO/IEC 10646-1. The required character set consists of all the characters in columns 002 through 007 of the “ISO-646 IRV” as defined above, except for lower-case letters. Table 1 - Character set features No. Description 2 Lower case characters a 3a 3b Number sign (#) OR Pound sign (£) 4a 4b Dollar sign ($) OR Currency sign (¤) 5a 5b Vertical bar (|) OR Exclamation mark (!) NOTE The feature numbering in this table is such as to maintain consistency with the first edition of IEC 61131-3,. a When lower-case letters (feature 2) are supported, the case of letters shall not be significant in language elements except within comments as defined in 2.1.5, string literals as defined in 2.2.2, and variables of type STRING and WSTRING as defined in 2.3.1. 2.1.2 Identifiers An identifier is a string of letters, digits, and underline characters which shall begin with a letter or underline character. The case of letters shall not be significant in identifiers, for example, the identifiers abcd, ABCD, and aBCd shall be interpreted identically. Underlines shall be significant in identifiers, for example, A_BCD and AB_CD shall be interpreted as different identifiers. Multiple leading or multiple embedded underlines are not allowed; for example, the character sequences __LIM_SW5 and LIM__SW5 are not valid identifiers. Trailing underlines are not allowed; for example, the character sequence LIM_SW5_ is not a valid identifier. Copyright International Electrotechnical Commission Provided by IHS under license with IEC Not for Resale No reproduction or networking permitted without license from IHS --``````-`-`,,`,,`,`,,`--- – 24 – 61131-3 IEC:2003(E) At least six characters of uniqueness shall be supported in all systems which support the use of identifiers, for example, ABCDE1 shall be interpreted as different from ABCDE2 in all such systems. The maximum number of characters allowed in an identifier is an implementation-dependent parameter. Identifier features and examples are shown in table 2. Download 1.35 Mb. Do'stlaringiz bilan baham: |
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