GS1 EPC Tag Data Standard 1.6 - Indicod-Ecr

46674668466946704671467246734674467546764677467846794680468146824683468446854686468746884689469046914692469346944695469646974698469947004701470247034704470547064707470847094710conversion. The number of bits to encode in this sequence is directly determined fromthe number of base-13 values being represented, as called for by the sum of the Prefixand Suffix Run lengths for base 13 sequences. The number of bits, for a given number ofBase 13 values, is determined from the Figure in Annex K. Next, an Extended-NonNumeric Base segment (either Base-40 or Base 84) is similarly encoded (if anyPrefix or Suffix Runs called for Extended-NonNumeric encoding).Next, a Base-10 Binary segment is encoded that directly represents the binary numberresulting from encoding the sequence of the digits in the Prefix and/or character mapand/or Suffix (ignoring any intervening non-digit characters) as a single value, or in otherwords, applying a base 10 to Binary conversion. The number of bits to encode in thissequence is directly determined from the number of digits being represented, as shown inAnnex K.Immediately after the last bit of the Base-10 bit sequence (if any), a non-numeric (Base30, Base 74, or Base 256) bit sequence is encoded (if the character map indicates at leastone non-numeric character). This bit sequence represents the binary number resultingfrom a base-30 to Binary conversion (or a Base-74 to Binary conversion, or a directtransfer of Base-256 values) of the sequence of non-digit characters in the data (ignoringany intervening digits). Again, the number of encoded bits is directly determined fromthe number of non-numeric values being represented, as shown in Annex K. Note that ifBase 256 was selected as the non-Numeric base, then the encoder is free to classify andencode each digit either as Base 10 or as Base 256 (Base 10 will be more efficient, unlessoutweighed by the ability to take advantage of a long Prefix or Suffix).Note that an Alphanumeric subsection ends with several variable-length bit fields (thecharacter map, and one or more Binary sections (representing the numeric and nonnumericBinary values). Note further that none of the lengths of these three variablelengthbit fields are explicitly encoded (although one or two Extended-Base Binarysegments may also be present, these have known lengths, determined from Prefix and/orSuffix runs). In order to determine the boundaries between these three variable-lengthfields, the decoder needs to implement a procedure, using knowledge of the remainingnumber of data bits, in order to correctly parse the Alphanumeric subsection. Anexample of such a procedure is described in Annex M.I.8.2.5 Padding the last ByteThe last (least-significant) bit of the final Binary segment is also the last significant bit ofthe Packed Object. If there are any remaining bit positions in the last byte to be filledwith pad bits, then the most significant pad bit shall be set to ‘1’, and any remaining lesssignificantpad bits shall be set to ‘0’. The decoder can determine the total number ofnon-pad bits in a Packed Object by examining the Length Section of the Packed Object(and if the Pad Indicator bit of that section is ‘1’, by also examining the last byte of thePacked Object).I.9 ID Map and Directory encoding optionsAn ID Map can be more efficient than a list of ID Values, when encoding a relativelylarge number of ID Values. Additionally, an ID Map representation is advantageous foruse in a Directory Packed Object. The ID Map itself (the first major subsection of everyID Map section) is structured identically whether in a Data or Directory IDMPO, but aCopyright ©2005- 2011 GS1 AISBL, All Rights Reserved. Page 184 of 218