ISO IEC 21471:2020 pdf free

ISO IEC 21471:2020 pdf free.Information technology一Automatic identification and data capture techniques
The finder pattern is a perimeter to the data region and is one module wide. Two adjacent sides, the left and lower sides, forming the L boundary, are solid dark lines; these are used primarily to determine physical size, orientation and symbol distortion. The two opposite sides are made up of alternating dark and light modules. These are used primarily to define the cell structure of the symbol, but also can assist in determining physical size and distortion. The extent of the quiet zone is indicated by the corner marks in Figure 1.
The data may be encoded using any combination of six encodation schemes (see Table 1). ASCII encodation is the basic scheme. All other encodation schemes are invoked from ASCII encodation and return to this scheme. The compaction efficiencies given in Table 1 need to be interpreted carefully.The best scheme for a given set of data may not be the one with the fewest bits per data character. If the highest degree of compaction is required, account has to be taken of switching between encodation schemes and between code sets within an encodation scheme (see Annex I). It should also be noted that even if the number of codewords is minimized, the codeword stream sometimes needs to be expanded to fill a symbol. This fill process is done using pad characters.
The default character interpretation for character values 0 to 127 shall conform to ISO/IEC 646. The default character interpretation for character values 128 to 255 shall conform to ISO 8859-1. The graphical representation of data characters shown throughout this document complies with the default interpretation. This interpretation can be changed using extended channel interpretation (ECI) escape sequences, see 5.4. The default interpretation corresponds to ECI 000003.
ASCII encodation is the default encodation scheme for the first symbol character in all symbol sizes. It encodes ASCII data, double density numeric data and symbology control characters. Symbology control characters include function characters, the pad character and the switches to other code sets. ASCII data is encoded as codewords 1 to 128 (ASCII value plus 1). Extended ASCII (data values 128 to 255) is encoded using the upper shift symbology control character (see 5.2.4.3). The digit pairs 00 to 99 are encoded with codewords 130 to 229 (numeric value plus 130). The ASCII code assignments are shown in Table 2.ISO IEC 21471 pdf free download.